Samacheer Kalvi Class 11 Bio Zoology Solutions Chapter 10 Neural Control and Coordination

Column I	Column II
1. Broca area	a. Perception of taste.
2. The pre-central gyrus	b. Voluntary movements
3. The postcentral gyrus	c. Aggression
4. Amygdala	d. Speech function

Answer: (c) I-d II-b III-a IV-c
In simple words: This match means: 1 (Broca area) is for d (Speech function), 2 (The pre-central gyrus) is for b (Voluntary movements), 3 (The postcentral gyrus) is for a (Perception of taste), and 4 (Amygdala) is for c (Aggression). These are different parts of the brain and their main jobs.

🎯 Exam Tip: Focus on linking specific brain regions with their primary functions, such as Broca's area for speech production and the pre-central gyrus for motor control.

 

Question 32. Assertion: Statement S – Brain controls emotions and feelings. Statement T – There are no sensory neurons in the brain. Hence it cannot sense the pain.
(a) Statement – S – True. Statement T – False
(b) Statement – S – True Statement T – True
(c) Statement – S – False Statement T – False
(d) Statement S – False Statement T – True
Answer: (b) Statement – S – True Statement T – True
In simple words: Both statements are true. The brain is definitely in charge of our feelings and emotions. Also, the brain itself does not have pain sensors, so it cannot feel pain directly, even during surgery.

🎯 Exam Tip: While the brain processes pain signals, its actual tissue lacks nociceptors, meaning it does not feel pain directly, a common misconception.

 

Question 33. Which is considered as the relay centre for impulses
(a) Medulla oblongata
(b) Cerebrum
(c) Hypothalamus
(d) Thalamus
Answer: (d) Thalamus
In simple words: The thalamus acts like a central station in the brain. It receives almost all sensory information, sorts it out, and then sends it to the correct parts of the cerebrum for processing.

🎯 Exam Tip: Visualize the thalamus as the "gateway to the cerebral cortex" for sensory information, except for the sense of smell.

 

Question 34. Which indicates A, B, C and D in the following diagram

(a) a) Temporal lobe b) Frontal lobe c) Parietal lobe d) Cerebellum
(b) a) Cerebellum b) Parietal lobe c) Temporal lobe d) Frontal lobe
(c) a) Cerebellum b) Frontal lobe c) Temporal lobe d) Parietal lobe
(d) a) Parietal lobe b) Cerebellum c) Frontal lobe d) Temporal lobe
Answer: (b) a) Cerebellum b) Parietal lobe c) Temporal lobe d) Frontal lobe
In simple words: In the diagram, label A points to the Cerebellum, B points to the Parietal lobe, C points to the Temporal lobe, and D points to the Frontal lobe. This option correctly identifies all these parts.

🎯 Exam Tip: Familiarize yourself with the anatomical locations of major brain structures, especially the cerebrum's lobes and the cerebellum.

 

Question 35. Find out the wrong statement.
(a) The pre-central gyrus is called a motor strip.
(b) The post-central gyrus is called a sensory strip.
(c) The medulla oblongata controls respiration.
(d) Wernicke area of the brain involved in the comprehension of speech.
Answer: (d) Wernicke area of the brain involved in the comprehension of speech.
In simple words: This statement is listed as the wrong one, meaning that Wernicke's area is NOT involved in speech comprehension. However, in biology, Wernicke's area IS known to be critical for understanding speech. This indicates a potential inaccuracy in the provided question or answer key.

🎯 Exam Tip: For brain function, Wernicke's area is correctly associated with language comprehension, while Broca's area is linked to language production. Be mindful of potential discrepancies in source material.

 

Question 36. The melatonin hormone which controls the sleep-wake cycle is secreted by
(a) Pineal body
(b) Thalamus
(c) Hypothalamus
(d) Medulla oblongata
Answer: (a) Pineal body
In simple words: The pineal gland makes melatonin, a hormone that helps regulate our body's sleep and wake cycles.

🎯 Exam Tip: Remember that the pineal gland is often called the "third eye" due to its role in regulating circadian rhythms with light and dark cycles.

 

Question 37. The lower portion of the midbrain consists of a pair of longitudinal nervous bands called
(a) Emotional brain
(b) Cerebral peduncles
(c) Pons
(d) Vermis
Answer: (b) Cerebral peduncles
In simple words: The bottom part of the midbrain has two long nerve bundles known as cerebral peduncles. These bundles help connect different parts of the brain.

🎯 Exam Tip: Knowing the specific structures in each brain region helps in understanding their functions and overall brain organization.

 

Question 38. The cauda equina presents in
(a) Cerebrum
(b) Thalamus
(c) Hippo cambus
(d) Spinal cord
Answer: (d) Spinal cord
In simple words: The cauda equina is a bundle of nerves found at the lower end of the spinal cord, looking like a horse's tail.

🎯 Exam Tip: Visualizing the "horse's tail" analogy can help remember the cauda equina's location and appearance.

 

Question 39. Match and find the correct answer.
i) Thalamus – A) Respiration Gastric Pits.
ii) Hypothalamus – B) Vision Hearing
iii) Mid brain – C) Satiety centre
iv) Medulla oblongata – D) Learning memory
Answer: a) i- D,ii – C,iii – B,iv – A
In simple words: The correct matches link the thalamus to learning, the hypothalamus to satiety, the midbrain to vision/hearing, and the medulla oblongata to breathing and stomach functions.

🎯 Exam Tip: For matching questions, eliminate obvious incorrect pairs first to narrow down the options. Each part of the brain has specific vital roles.

 

Question 40. The cluster of nerve tissue in the cell body of neurons are called as
(a) Gyri
(b) Sulci
(c) Vermis
(d) Nerve ganglion.
Answer: (d) Nerve ganglion.
In simple words: A group of nerve cells bundled together in the cell body of neurons is called a nerve ganglion.

🎯 Exam Tip: Understand the difference between nerve fibers, nerve cell bodies, and their organized clusters like ganglia.

 

Question 41. Find out the wrong pair
(a) Cervical nerve – 8 pairs
(b) Thoracic nerve – 12 pairs
(c) Sacrum nerve – 4 pairs
(d) Coccyx nerve – 1 pair
Answer: (c) Sacrum nerve – 4 pairs
In simple words: The sacral nerves usually come in 5 pairs, not 4. The other pairs listed are correct for cervical, thoracic, and coccygeal nerves.

🎯 Exam Tip: Memorize the number of pairs for each type of spinal nerve as this is a common factual question.

 

Question 42. What is the amount of cerebrospinal fluid secreted in an adult?
(a) 500 ml
(b) 150 ml
(c) 400 ml
(d) 250 ml
Answer: (b) 150 ml
In simple words: In an adult, about 150 ml of cerebrospinal fluid is present at any given time, which constantly circulates and gets replaced.

🎯 Exam Tip: Note the difference between the amount secreted daily (around 500 ml) and the total volume present at one time (around 150 ml).

 

Question 43. The dissolved nicotene and alcohol in …………………… and ………………… minutes reach the brain.
(a) 7 and 8 minutes
(b) 6 and 7 minutes
(c) 7 seconds and 6 minutes
(d) 7 and 5 minutes.
Answer: (c) 7 seconds and 6 minutes
In simple words: Nicotine reaches the brain in about 7 seconds, and alcohol reaches it in about 6 minutes, showing how quickly these substances affect the nervous system.

🎯 Exam Tip: Pay close attention to units (seconds vs. minutes) when dealing with time-related biological processes.

 

Question 44. Name the structure that regulates homeostasis.
(a) Mammillary body
(b) Pineal body
(c) Hypothalamus
(d) Pituitary.
Answer: (c) Hypothalamus
In simple words: The hypothalamus is the part of the brain that controls many body functions to keep everything balanced and stable, like temperature and hunger.

🎯 Exam Tip: Homeostasis is a key function of the hypothalamus; connect this brain part directly to maintaining the body's internal balance.

 

Question 45. What is brain stem.
(a) The structure seen in between spinal cord and cerebellum.
(b) The region between Diencephalon and spinal cord
(c) The region between medulla oblongata and cerebrum.
(d) The region between medulla oblongata and mid-brain.
Answer: (b) The region between Diencephalon and spinal cord
In simple words: The brain stem is the lower part of the brain that connects the cerebrum and cerebellum to the spinal cord. It controls many basic life functions.

🎯 Exam Tip: The brain stem is vital for basic survival functions like breathing and heart rate, acting as a critical bridge for nerve signals.

 

Question 46. What is the function of corpora quadri gemina?
(a) Vision and hearing
(b) Vision and homeostasis
(c) Hearing and sense of touch
(d) Hearing and vomiting.
Answer: (a) Vision and hearing
In simple words: The corpora quadrigemina are four small bumps on the back of the midbrain that help process visual and auditory information.

🎯 Exam Tip: Remember that "quadri" refers to four, corresponding to the four colliculi (superior for vision, inferior for hearing) that make up this structure.

 

Question 47. The region seen in the mid of cerebellum.
(a) Corpus callosum
(b) Pineal body
(c) Pituitary
(d) Vermis.
Answer: (d) Vermis.
In simple words: The vermis is a narrow, worm-like part located in the middle of the cerebellum, connecting its two hemispheres.

🎯 Exam Tip: The vermis is crucial for coordinating body movements, especially those related to posture and gait.

 

Question 48. What is the function of the interneuron?
(a) Impulses from afferent and efferent neurons.
(b) Impulses transmitted from efferent neurons to afferent neurons.
(c) Impulses transmitted from central nervous system to receptor organs
(d) From nerve transmitters to the spinal cord
Answer: (a) Impulses from afferent and efferent neurons.
In simple words: Interneurons act like a bridge, connecting sensory (afferent) neurons to motor (efferent) neurons within the central nervous system. They help process information.

🎯 Exam Tip: Interneurons are often involved in complex processing and reflexes, acting as intermediaries between input and output neurons.

 

Question 49. Which part of the brain controls the unconditioned reflux?
(a) The cortex of cerebrum
(b) The medulla of brain
(c) Cerebellum
(d) pons.
Answer: (a) The cortex of cerebrum
In simple words: The cerebral cortex, which is the outer layer of the cerebrum, plays a role in controlling basic, automatic reflexes that we don't need to learn.

🎯 Exam Tip: While simple reflexes are often handled at the spinal cord level, the cerebral cortex can also influence or modulate unconditioned reflexes.

 

Question 50. ……………………..pair of nerves from cranium and …………………….. pair of nerves from spinal cord
(a) 10 and 31
(b) 12 and 31
(c) 31 and 12
(d) 31 and 10.
Answer: (b) 12 and 31
In simple words: Humans have 12 pairs of cranial nerves that come from the brain and 31 pairs of spinal nerves that branch out from the spinal cord.

🎯 Exam Tip: Always remember the exact numbers: 12 pairs of cranial nerves and 31 pairs of spinal nerves are fundamental facts about the nervous system.

 

Question 51. How much cerebrospinal fluid is synthesized in adults?
(a) 200ml
(b) 300ml
(c) 150ml
(d) 100ml.
Answer: (c) 150ml
In simple words: About 150ml of cerebrospinal fluid is made and kept in the brain and spinal cord to protect them. The body produces about 500ml daily, but the total volume at one time is 150ml.

🎯 Exam Tip: Distinguish between the total volume of CSF present (around 150ml) and the daily production rate (around 500ml) when answering.

 

Question 52. What is the function of vagus nerve?
(a) It regulates the function of abdominal structure
(b) It regulates the speech and swallowing
(c) It regulates the homeostasis of the body
(d) Taste perception
Answer: (a) It regulates the function of abdominal structure
In simple words: The vagus nerve helps control many organs in the chest and abdomen, like the heart, lungs, and digestive system. It helps keep these parts working correctly.

🎯 Exam Tip: The vagus nerve is the longest cranial nerve and is crucial for the parasympathetic nervous system, influencing heart rate, digestion, and more.

 

Question 53. Name the neural system which is auto functioning and self-governed.
(a) Somatic neural system
(b) Automatic neural system
(c) Peripheral neural system
(d) Limbic system.
Answer: (b) Automatic neural system
In simple words: The "automatic neural system," also known as the autonomic nervous system, controls body functions that happen without us thinking about them, like breathing and heart rate.

🎯 Exam Tip: The autonomic nervous system is divided into sympathetic (fight or flight) and parasympathetic (rest and digest) branches, both operating automatically.

 

Question 54. Name the structure that regulates the autonomic neural system.
(a) Cerebrum
(b) Cerebellum
(c) Hypothalamus
(d) Pons.
Answer: (c) Hypothalamus
In simple words: The hypothalamus is like the main control center for the automatic nervous system. It helps manage things like body temperature, thirst, and hunger without us having to think about it.

🎯 Exam Tip: The hypothalamus plays a central role in maintaining overall body balance and coordinating internal organ functions.

 

Question 55. Name the lubricating fluid which is secreted from the gland present at the base of the eyelashes.
(a) Lacrymal gland
(b) Cerebro-spinal fluid
(c) Thymus gland
(d) Sebaceous glands.
Answer: (d) Sebaceous glands.
In simple words: Tiny sebaceous glands at the base of our eyelashes make an oily fluid that keeps the eyelids moist and lubricated. This is similar to oil glands on skin.

🎯 Exam Tip: The Meibomian glands are a type of sebaceous gland found in the eyelids, contributing to the oily layer of tears.

 

Question 56. Find the ABC and D in the diagram
(a) a) Tear duct b) Sciera c) Iris d) Tear gland
(b) a) Sciera b) Iris c) Tear gland d)Tear duct
(c) a) Tear duct b) Iris c) Sclerad d)lTear duct
(d) a) Tear gland b) Sclera c) Tear duct d) Iris.
Answer: (d) a) Tear gland b) Sclera c) Tear duct d) Iris.
In simple words: In the diagram, 'A' points to the tear gland, 'B' points to the white part of the eye called the sclera, 'C' points to the tear duct, and 'D' points to the colored part of the eye, the iris.

🎯 Exam Tip: Carefully observe the lines in the diagram to identify which structure each letter points to, and match them with the correct anatomical names.

 

Question 57. Name the tissue which forms the non-vascular transparent coat cornea
(a) Stratified squamous epithelium
(b) Squamous epithelium
(c) Canal of schlemm
(d) All the above.
Answer: (a) Stratified squamous epithelium
In simple words: The clear outer layer of the eye, called the cornea, is made of stratified squamous epithelium, a type of tissue that helps it be transparent and protective.

🎯 Exam Tip: The cornea's avascular nature means it gets nutrients from tears and aqueous humor, which is crucial for its transparency.

 

Question 58. Assertion: In bright light the circular muscle in the iris contract so that the size of the pupil decreases and the light enter is regulated Reason: In dim light, the radial muscle contract the pupil size increases and less light enters the eye.
(a) The assertion true: but reason wrong
(b) The assertion and reason are true
(c) The assertion is true but reason does not explain the assertion
(d) The assertion and reason are wrong.
Answer: (a) The assertion true: but reason wrong
In simple words: The assertion is true because in bright light, the circular muscles of the iris shrink, making the pupil smaller to control light. However, the reason is false because in dim light, radial muscles contract to make the pupil larger, allowing more light to enter, not less.

🎯 Exam Tip: Understand the dual action of circular and radial muscles in the iris to control pupil size: circular muscles constrict the pupil, and radial muscles dilate it.

 

Question 59. Name the yellow flat spot at the centre of the posterior region of the retina.
(a) Blind spot
(b) Scelera
(c) Iris
(d) Maculalutea
Answer: (d) Maculalutea
In simple words: The yellow, flat area in the middle of the back of the retina is called the macula lutea. This area is responsible for sharp, detailed central vision.

🎯 Exam Tip: The macula lutea contains the fovea centralis, which has the highest concentration of cones for acute vision.

 

Question 60. Which colour is perceived through chloropsin is sensitive to the medium wavelength of 530 mm
(a) Red cones
(b) Green cones
(c) Blue cones
(d) Red cells.
Answer: (b) Green cones
In simple words: Chloropsin is a pigment found in green cones, which are special cells in our eyes that help us see green colors at a wavelength of 530 nm.

🎯 Exam Tip: Remember the three types of cones (red, green, blue) and their respective photopigments for different color perceptions.

 

Question 61. Name the glands that secrete tear.
(a) Lacrymal gland
(b) Sebaceous gland
(c) Mandibular gland
(d) Choroid plexues
Answer: (a) Lacrymal gland
In simple words: The lacrimal glands, located above our eyes, produce tears to keep our eyes moist and clean.

🎯 Exam Tip: Tears also contain protective enzymes like lysozyme, which help fight off bacteria.

 

Question 62. …………………… enzyme is present in the tear.
(a) Ptyalin
(b) Lysozyme
(c) Lipase
(d) Erypsin.
Answer: (b) Lysozyme
In simple words: Tears contain an enzyme called lysozyme. This enzyme helps protect our eyes by breaking down harmful bacteria.

🎯 Exam Tip: Lysozyme is a natural antibiotic found in various body secretions, highlighting the body's built-in defense mechanisms.

 

Question 63. Name the structure where more cones present.
(a) Foveacenlralis
(b) Maculalutea
(c) Retina
(d) Blind spot.
Answer: (a) Foveacenlralis
In simple words: The fovea centralis, located within the macula, has the highest number of cone cells. This area is responsible for our sharpest vision.

🎯 Exam Tip: The fovea centralis is the area of highest visual acuity, where the image is focused when we look directly at an object.

 

Question 64. What is tectorial membrane?
(a) A roof like structure over hanging the organ of corti through out its length with the stiff gel membrane called tectorial membrane.
(b) A roof like structure over hanging the organ of corti through out its length with the stiff gel membrane called tactoreal membrane.
(c) A roof like structure over hanging the organ of corti through out its length with the stiff gel membrane called tectoreal membrane.
(d) A roof like structure over hanging the organ of corti through out its length with the stiff gel membrane called tectorial membrane.
Answer: (a) A roof like structure over hanging the organ of corti through out its length with the stiff gel membrane called tectorial membrane.
In simple words: The tectorial membrane is a stiff, gel-like structure that sits like a roof over the hair cells in the organ of Corti in the inner ear. It plays a role in hearing.

🎯 Exam Tip: During sound reception, the hair cells in the organ of Corti bend against the tectorial membrane, generating nerve impulses.

 

Question 65. The concave lens helps in correct ………………. defect
(a) Myopia
(b) Hyper metropia
(c) Astigmatism
(d) Presbiopia
Answer: (a) Myopia
In simple words: A concave lens is used to correct myopia, which is also known as nearsightedness. It helps focus light properly on the retina.

🎯 Exam Tip: Remember that concave lenses diverge light, extending the focal point to reach the retina in myopic eyes.

 

Question 66. Which of the defect is depicted in the following diagram:
(a) Emmetropia
(b) Myopia
(c) Hypermetropia
(d) Astigmatism.
Answer: (b) Myopia
In simple words: The diagram shows how light focuses in front of the retina, which is the problem seen in myopia or nearsightedness. This causes distant objects to appear blurry.

🎯 Exam Tip: In myopia, the eyeball is typically too long, or the cornea is too curved, causing light to converge too soon.

 

Question 67. Match and find the correct sequence.

(a) 1 -a 2-b 3-c 4-c
(b) 1 -d 2-b 3-a 4-c
(c) 1-d 2-a 3-a 4-b
(d) 1-d 2-c 3-b 4-c
Answer: (b) 1 -d 2-b 3-a 4-c
In simple words: Concave lenses fix myopia. Convex lenses fix hypermetropia. Cataracts are treated with surgery. Cylindrical lenses are used for astigmatism.

🎯 Exam Tip: Create a table or flashcards to remember which lens type corrects which eye defect and the treatment for conditions like cataracts.

 

Question 68. Name the organ which regulates vision perception and homeostasis.
(a) Ear
(b) Eye
(c) Cerebrum
(d) Cerebellum.
Answer: (a) Ear
In simple words: The ear helps with more than just hearing; it also contains structures that regulate balance and body position, which is part of maintaining homeostasis.

🎯 Exam Tip: Remember the inner ear's role in balance (vestibular system), which contributes to the body's overall equilibrium and homeostasis.

 

Question 69. Find out the wrong pair.
(a) Pinna – Eardrum
(b) Oval window – Round window
(c) Cochlea – Malleus
(d) Perilymph – Endolymph
Answer: (c) Cochlea – Malleus
In simple words: The cochlea is a part of the inner ear that helps with hearing, while the malleus is one of the three tiny bones (ossicles) in the middle ear. They are not directly paired in function or location like the other options.

🎯 Exam Tip: Differentiate between the structures of the outer, middle, and inner ear. The malleus, incus, and stapes are ossicles of the middle ear.

 

Question 70. Indicate ABC and D in the Diagram.
(a) a) Incus b) Eardrum c) Organ of Corti d) Tectorial membrane.
(b) a) Organ of Corti b) Incus c) Tectorial membrane d)Eardrum
(c) a) Eardrum b) Incus c) Organ of Corti d) Tectorial membrane
(d) a) Eardrum b) Incus
Answer: (c) a) Eardrum b) Incus c) Organ of Corti d) Tectorial membrane
In simple words: In the diagram of the ear, 'A' points to the eardrum (tympanum), 'B' points to the incus bone, 'C' points to the organ of Corti, and 'D' points to the tectorial membrane.

🎯 Exam Tip: Be precise when identifying labeled parts in diagrams; closely trace the lines from the labels to the specific structures.

 

Question 71. Find out the wrong statement.
(a) The equilibrium receptor regions called maculae are involved in detecting the linear movement of the head.
(b) The otoliths are made up of calcium
(c) The crista ampullaris is to detect rotational movement of the head
(d) Severe hearing loss occurs with frequent exposure to sound with intensities greater than50db.
(The 90db will affect the hearing).
Answer: (d) Severe hearing loss occurs with frequent exposure to sound with intensities greater than50db.
In simple words: The statement about 50dB causing severe hearing loss is wrong; prolonged exposure to sounds much louder, specifically above 85-90 dB, is what typically causes hearing damage. The other statements about maculae, otoliths, and crista ampullaris are correct.

🎯 Exam Tip: Understand the safe limits for sound exposure; sustained noise above 85-90 dB can lead to permanent hearing damage.

 

Question 72. A person on his way to a village in a car for weekend holidays after finishing the office work. As he is very tired he begins to feel drowsy. He turns up the car stereo volume opens the car window and has sips ice-cold water. How do these actions keep him awake? The increase in the number of sensory stimuli he received is relayed to the cerebral cortex which gets activated and prevents sleeping,
(a) Spinal cord
(b) Cerebrum
(c) Medulla oblongata
(d) Cerebellum.
Answer: (c) Medulla oblongata
In simple words: The increase in sensory input from loud music, cold air, and sips of cold water all send signals to the brain. This heightened sensory information goes to the cerebral cortex, which then becomes more active and helps to prevent drowsiness. The medulla oblongata is a key part of the brainstem that connects to higher brain centers and processes these signals.

🎯 Exam Tip: Recognize that multiple sensory inputs can work together to increase brain alertness by stimulating the cerebral cortex and reticular activating system.

 

Question 73. Name the structure that connects the middle ear and pharynx.
(a) Eustachian tube
(b) Middle ear
(c) Oval window
(d) Organ of the cortii.
Answer: (a) Eustachian tube
In simple words: The Eustachian tube is a small passage that links the middle ear to the back of the throat, helping to balance air pressure. It opens when you swallow or yawn.

🎯 Exam Tip: Remember the Eustachian tube is crucial for equalizing pressure, preventing discomfort, especially during changes in altitude.

 

Question 74. Which part of the ear have bony labyrinth and membranous labyrinth?
(a) External ear
(b) Inner ear
(c) Middle ear
(d) None of the options
Answer: (b) Inner ear
In simple words: The inner part of your ear has two complex systems, the bony labyrinth and the membranous labyrinth, which work together for hearing and balance. These structures are nestled deep inside the skull.

🎯 Exam Tip: The inner ear is often referred to as the labyrinth due to its intricate, maze-like structure.

 

Question 75. Name the structure present in the bony labyrinth.
(a) Cochlea, vestibule, maleus
(b) Cochlea, vestibule Incus
(c) Cochlea semicircular canals, stapes
(d) Cochlea, vestibule semicircular canals.
Answer: (d) Cochlea, vestibule semicircular canals.
In simple words: The bony labyrinth holds three main parts: the cochlea for hearing, and the vestibule and semicircular canals for balance. These fluid-filled areas are essential for how we hear and stay upright.

🎯 Exam Tip: When remembering the bony labyrinth components, focus on its roles in both hearing (cochlea) and balance (vestibule, semicircular canals).

 

Question 76. Where is the stereo cilia cells present in the ear?
(a) Scala media
(b) Scala vestibuli
(c) Scala tymnani
(d) Middle ear.
Answer: (a) Scala media
In simple words: Stereocilia, which are tiny hair-like structures, are found in the scala media of the inner ear. These cells are key for changing sound vibrations into electrical signals that the brain can understand.

🎯 Exam Tip: Stereocilia are vital sensory receptors, playing a critical role in the mechanotransduction of sound in the ear.

 

Question 77. Match and find the correct sequence.
I. Meissner’s corpuscles a) continuous pressure
II. Pacinian corpuscles b) hardness, pain
III. Ruffini endings c) temperature
IV. Krause and bulbs d) light pressure
Answer: (c) I-d, II-b, III-a, IV-c
In simple words: Meissner's corpuscles feel light touch, Pacinian corpuscles sense strong pressure and pain, Ruffini endings respond to continuous pressure, and Krause end bulbs detect cold temperatures. Each of these tiny parts in our skin helps us feel different things.

🎯 Exam Tip: To remember the sensory receptors, link each one to its primary function: Meissner's for light touch, Pacinian for deep pressure, Ruffini for stretch/sustained pressure, and Krause for cold.

 

Question 78. When a cockroach tries to enter into the ear of a sleeping person, which one of the following process will start?
(a) Unconditioned reflex
(b) Neuro muscular fatigue
(c) Stimulation of negative feedback mechanism
(d) conditioned reflex
Answer: (a) Unconditioned reflex
In simple words: An unconditioned reflex is an automatic and natural reaction to something, like a sudden jolt from a cockroach. It does not need to be learned.

🎯 Exam Tip: Unconditioned reflexes are innate responses that happen without prior learning or experience, providing immediate protection.

 

Question 79. What is the number of nerve cells present in the brain
(a) 90 million
(b) 100 billion
(c) 90 billion
(d) 100 million
Answer: (b) 100 billion
In simple words: The human brain has about 100 billion nerve cells, also called neurons, which are responsible for all its functions. These many cells allow for complex thoughts and actions.

🎯 Exam Tip: Remember the vast number of neurons (billions) in the brain, highlighting its incredible complexity and processing power.

II. Write Very Short Answer

 

Question 1. What are the two branches of human nervous system?
Answer: The two main branches of the human nervous system are the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The CNS includes the brain and spinal cord, while the PNS consists of all other nerves.
In simple words: The human nervous system has two main parts: the Central Nervous System (brain and spinal cord) and the Peripheral Nervous System (all other nerves).

🎯 Exam Tip: Clearly distinguish between the CNS (brain and spinal cord) and the PNS (all nerves outside the CNS) as fundamental divisions.

 

Question 2. What is meant by Neuroglia? What are its functions?
Answer: Neuroglia are special non-nervous cells that provide support to the nervous tissue. They play several important roles, including nourishing neurons, helping to repair injured tissues, and assisting in cell division and regeneration. Neuroglia also act as phagocytic cells, engulfing foreign particles during any brain injury to protect the brain.
In simple words: Neuroglia are support cells in the nervous system. They feed nerves, fix damaged areas, help with new cell growth, and clean up foreign particles in the brain.

🎯 Exam Tip: Remember that neuroglia are the "support staff" of the nervous system, crucial for neuron health and brain protection, unlike neurons which transmit signals.

 

Question 3. Differentiate the functions of myelinated and non-myelinated neurons.
Answer:

In simple words: Myelinated neurons send signals fast and are found in the brain's medulla, while non-myelinated neurons send signals slowly and are in the brain's outer layer, the cerebrum.

🎯 Exam Tip: The presence of a myelin sheath is the key difference, directly impacting the speed of nerve impulse conduction and location in the brain.

 

Question 4. Give notes on (a) Synaptic Knob (b) Neurotransmitters (c) Inter neural space.
Answer:
(a) Synaptic Knob: This is the bulb-like, distant end of an axon, where nerve impulses are transmitted to another neuron. It acts as the terminal point for communication.
(b) Neurotransmitters: These are chemical messengers stored inside synaptic vesicles within the synaptic knob. They are released to transmit signals across the synapse.
(c) Inter neural space: Also known as the synaptic cleft, this is the small gap between the presynaptic neuron (sending neuron) and the postsynaptic neuron (receiving neuron) where neurotransmitters travel.
In simple words: The synaptic knob is the end of a nerve that sends signals. Neurotransmitters are chemicals inside tiny sacs that carry these signals. The inter neural space is the small gap between two nerves where the signals cross.

🎯 Exam Tip: Understand the sequence: impulse reaches synaptic knob, neurotransmitters are released into the inter neural space, and then bind to the next neuron.

 

Question 5. What is meant by nerve impulses?
Answer: A nerve impulse is an electrical signal that travels along a nerve fiber. It is a rapid change in the electrical potential across the membrane of a neuron, allowing information to be carried throughout the body.
In simple words: A nerve impulse is an electrical message that moves along a nerve, carrying information quickly from one part of the body to another.

🎯 Exam Tip: Define nerve impulses as electrical signals for full marks, highlighting their role in communication.

 

Question 6. What is meant by resting potential?
Answer: Resting potential is the electrical potential difference that exists across the plasma membrane of a neuron when it is not actively transmitting a nerve impulse. In this state, the inside of the neuron is typically more negative than the outside.
In simple words: Resting potential is the electrical charge difference across a nerve cell's wall when it is not sending a message. The inside is usually negative compared to the outside.

🎯 Exam Tip: Emphasize that resting potential is the stable, inactive electrical state of a neuron, maintained by ion pumps.

 

Question 7. What is meant by threshold potential?
Answer: Threshold potential is the specific level of membrane potential that must be reached during depolarization for an action potential to be triggered. Once enough \( \text{Na}^+ \) ions enter the cell, the membrane potential rapidly rises to this critical point, usually around \( -55 \text{ mV} \), causing the nerve to fire.
In simple words: Threshold potential is the trigger point a nerve cell must reach to fire an electrical signal. If the electrical charge inside the cell hits a certain level, the signal will be sent.

🎯 Exam Tip: Highlight that threshold potential is an "all-or-none" phenomenon; if it's not reached, no action potential occurs.

 

Question 8. What is threshold stimulus?
Answer: The threshold stimulus is the minimum strength of a stimulus required to cause a neuron's membrane potential to reach the threshold potential. This is the point at which an action potential will be generated.
In simple words: Threshold stimulus is the smallest push or signal needed to make a nerve cell fire an electrical message. If the push is too weak, nothing happens.

🎯 Exam Tip: Connect threshold stimulus directly to threshold potential; one leads to the other for nerve impulse generation.

 

Question 9. What is meant by all or none principle?
Answer: The all-or-none principle states that an action potential will either occur completely or not at all. If a stimulus reaches the threshold potential, a full-strength action potential is generated; if it does not, no action potential is produced, regardless of the stimulus strength below the threshold.
In simple words: The all-or-none principle means a nerve signal either happens fully or not at all. There is no such thing as a "small" or "large" nerve signal, only "on" or "off."

🎯 Exam Tip: Explain that the "all or none" principle means nerve impulses do not vary in strength once the threshold is met; they either fire completely or not at all.

 

Question 10. What is the cause of brain tumours?
Answer: Brain tumors often arise from glial cells because, unlike nerve cells (neurons) which do not divide, glial cells retain their ability to undergo cell division. This means that if glial cells lose control of their growth, they can multiply rapidly, leading to the formation of most brain tumors of neural origin.
In simple words: Brain tumors often happen when brain support cells called glial cells start dividing without stopping. Regular nerve cells don't divide, so they don't usually cause tumors.

🎯 Exam Tip: Note that brain tumors primarily originate from glial cells due to their retained mitotic activity, a key distinguishing factor from mature neurons.

 

Question 11. What are meninges?
Answer: Meninges are the three protective membranes that surround the brain and spinal cord. These layers, from outermost to innermost, are the dura mater, arachnoid mater, and pia mater. Their primary role is to provide a protective barrier against physical trauma.
In simple words: Meninges are three protective layers that cover the brain and spinal cord. They are like a shield, keeping these important parts safe.

🎯 Exam Tip: List the three layers of meninges (dura mater, arachnoid mater, pia mater) and their primary function as protection for the central nervous system.

 

Question 12. What is meant by lazy gate?
Answer: During hyperpolarization, the \( \text{K}^+ \) ion gates remain more permeable to \( \text{K}^+ \) even after the membrane potential has returned to the resting threshold level. These gates close slowly, causing a temporary overshot of the resting potential, and this delayed closing action leads them to be termed "lazy gates."
In simple words: Lazy gates are like slow-closing doors for potassium ions in a nerve cell. They stay open a bit too long after a signal, making the cell extra negative for a short time before it fully rests.

🎯 Exam Tip: Connect "lazy gate" with the slow closing of \( \text{K}^+ \) channels, which causes hyperpolarization by allowing excess potassium to leave the cell.

 

Question 13. What is spike potential?
Answer: Spike potential is the rapid, sharp increase in membrane potential that occurs during an action potential. It is caused by a swift influx of \( \text{Na}^+ \) ions into the neuron, which quickly changes the membrane potential to a positive value, typically up to about \( +45 \text{ mV} \). This quick rise is essential for transmitting nerve signals.
In simple words: Spike potential is the fast, sudden jump in a nerve cell's electrical charge when it sends a signal. It happens when sodium ions quickly rush in, making the inside positive.

🎯 Exam Tip: Remember that spike potential is characterized by the rapid depolarization phase of an action potential, driven by \( \text{Na}^+ \) influx.

 

Question 14. What is meant by repolarisation?
Answer: Repolarization is the process where the neuron's membrane potential returns to its negative resting state after depolarization. This occurs when \( \text{K}^+ \) ion channels open, allowing potassium ions to flow out of the axolemma, reducing the positive charge inside the cell and restoring the negative potential.
In simple words: Repolarization is when a nerve cell's electrical charge goes back to normal after sending a signal. Potassium ions leave the cell, making the inside negative again.

🎯 Exam Tip: Understand repolarization as the recovery phase where potassium outflow restores the negative resting membrane potential.

 

Question 15. What is Hyper polarisation?
Answer: Hyperpolarization occurs when the repolarization process causes the membrane potential to become even more negative than the normal resting potential, typically dropping from \( -70 \text{ mV} \) to about \( -90 \text{ mV} \). This temporary over-negativity makes it harder for the neuron to fire another action potential immediately.
In simple words: Hyperpolarization is when a nerve cell's charge becomes extra negative, even more than its usual resting state. This makes it harder for the cell to send another message right away.

🎯 Exam Tip: Hyperpolarization serves as a brief refractory period, preventing immediate re-excitation of the neuron after an action potential.

 

Question 16. Which decides the speed of the conduction of a nerve impulse?
Answer: The speed at which a nerve impulse is conducted along an axon is primarily determined by two factors: the diameter of the axon and the presence of myelination. A larger axon diameter allows for faster conduction due to less resistance, and myelinated axons transmit impulses much faster than non-myelinated ones because the myelin sheath enables saltatory conduction.
In simple words: The speed of a nerve signal depends on how wide the nerve fiber is and if it has a special coating called myelin. Wider fibers and those with myelin send signals faster.

🎯 Exam Tip: The two key factors affecting nerve impulse speed are axon diameter (larger is faster) and myelination (myelinated is faster due to saltatory conduction).

 

Question 17. What is septum pellucidum?
Answer: The septum pellucidum is a thin, translucent membrane located in the brain that separates the lateral ventricles, specifically the first and second ventricles. This structure serves as a partition, contributing to the overall organization of the brain's ventricular system.
In simple words: The septum pellucidum is a thin sheet inside the brain that divides the two main fluid-filled spaces, called ventricles.

🎯 Exam Tip: Remember the septum pellucidum as the delicate membrane separating the lateral ventricles, crucial for ventricular anatomy.

 

Question 18. What is the difference between sub durai space and sub arachnoid space
Answer:

In simple words: The sub dural space is a tiny gap between two brain coverings, the arachnoid and dura mater. The sub arachnoid space is found between the arachnoid and pia mater, and it contains cerebrospinal fluid.

🎯 Exam Tip: Clearly define the location of each space relative to the meningeal layers for precise differentiation.

 

Question 19. What is meant by sulcus and gyrus? What is its functions.
Answer: The surface of the cerebrum in the brain is characterized by folds and grooves. Gyri are the raised ridges or convolutions seen on the cerebrum, while sulci are the shallow grooves that separate these gyri. The primary function of both gyri and sulci is to significantly increase the surface area of the cerebral cortex, allowing for a greater number of neurons and more complex cognitive functions to be packed into the skull.
In simple words: Gyri are the raised bumps, and sulci are the dips on the brain's surface. They both help to make the brain bigger on the inside so it can hold more thinking cells.

🎯 Exam Tip: Highlight that gyri (ridges) and sulci (grooves) are essential for maximizing the cerebral cortex's surface area, which enhances brain function.

 

Question 20. Name the lobes of cerebrum?
Answer: The cerebrum is divided into four main lobes, each responsible for different functions. These lobes are:
1. Frontal lobe
2. Parietal lobe
3. Temporal lobe
4. Occipital lobe
In simple words: The cerebrum, which is the largest part of the brain, is split into four main sections: the frontal, parietal, temporal, and occipital lobes. Each section handles different tasks.

🎯 Exam Tip: Memorize the four major lobes of the cerebrum (frontal, parietal, temporal, occipital) and their general functions for a comprehensive understanding.

 

Question 21. What is the function of proca?
Answer: The area referred to as "proca" (likely Broca's area) is critically involved in speech production. It plays a key role in the motor aspects of language, enabling us to form and articulate words.
In simple words: The "proca" (Broca's) area helps us speak. It controls the movements needed to make words with our mouth.

🎯 Exam Tip: Associate Broca's area with the motor control of speech, emphasizing its role in language expression rather than comprehension.

 

Question 22. What is meant by a blood brain barrier.
Answer: The blood-brain barrier is a highly selective semipermeable border of endothelial cells that prevents many foreign substances in the bloodstream from entering the brain. It acts as a protective mechanism, carefully regulating which molecules can pass from the blood into the delicate brain tissue.
In simple words: The blood-brain barrier is a special shield around the brain that stops harmful things in the blood from getting into the brain. It lets good things pass but blocks bad ones.

🎯 Exam Tip: Define the blood-brain barrier as a protective filter, regulating substance entry into the brain from the bloodstream.

 

Question 23. Which part of the cerebrum is called as sheet of emotions?
Answer: The cortex of the parietal, occipital, and temporal lobes of the cerebrum are collectively involved in processing and interpreting emotions, and in some contexts, can be considered as contributing to the "sheet of emotions." These areas integrate various sensory inputs and play a role in emotional responses.
In simple words: The outer layers of the parietal, occipital, and temporal parts of the brain work together to handle emotions.

🎯 Exam Tip: While emotions involve complex brain networks, remember that multiple cortical regions, including parietal, occipital, and temporal lobes, contribute to emotional processing.

 

Question 24. What is meant by motor area?
Answer: The motor area of the brain is responsible for controlling voluntary muscular movements. It is primarily located in the posterior part of the frontal lobes. This area receives and interprets sensory impulses, then generates the commands necessary for conscious muscle actions.
In simple words: The motor area in the front of your brain tells your muscles how to move when you want them to. It takes in messages from your senses and then makes your body act.

🎯 Exam Tip: Associate the motor area with voluntary movement control, located in the frontal lobe, and its role in converting sensory input into motor output.

 

Question 25. What is the function of association area?
Answer: Association areas in the brain are cortical regions that integrate information from different sensory and motor areas. They are crucial for higher-level cognitive functions, including memory, complex communications, learning, and reasoning. These areas link various types of information to form coherent thoughts and actions.
In simple words: Association areas in the brain help us with thinking, learning, remembering, and talking. They combine different kinds of information to help us understand things better.

🎯 Exam Tip: Recognize association areas as the centers for complex cognitive functions, linking sensory and motor information for higher thought processes.

 

Question 26. Where is pineal body situated? What is its functions?
Answer: The pineal body is a small endocrine gland situated behind the choroid plexus, where the epithalamus forms a short stalk. Its primary function is to secrete the hormone melotonin (melatonin), which plays a crucial role in regulating the body's sleep-wake cycle, also known as circadian rhythm.
In simple words: The pineal body is a tiny gland in the brain that makes a hormone called melatonin. This hormone helps control when we feel sleepy and when we feel awake, keeping our body clock on track.

🎯 Exam Tip: Key points for the pineal body are its location (epithalamus) and its secretion of melatonin, which regulates the sleep-wake cycle.

 

Question 27. For a man to live all parts of the brain is important. How is brain divided into?
Answer: For a person to live and function, all parts of the brain are vital, as each contributes to essential processes. The brain is broadly divided into several key regions, each with specialized roles. These include:
- Cerebrum
- Thalamus
- Hypothalamus
- Pons
- Cerebellum
- Medulla oblongata
In simple words: All parts of the brain are important for living. The brain is divided into main sections like the cerebrum, thalamus, hypothalamus, pons, cerebellum, and medulla oblongata.

🎯 Exam Tip: List the major divisions of the brain and briefly recall one function for each to demonstrate understanding of their collective importance.

 

Question 28. What is meant by corpus callosum?
Answer: The corpus callosum is a large, thick band of nerve fibers that connects the two cerebral hemispheres of the brain. Its main function is to allow communication and information exchange between the left and right sides of the brain, enabling coordinated thought and action.
In simple words: The corpus callosum is a thick bridge of nerves that connects the two halves of the brain. It helps both sides talk to each other and work together.

🎯 Exam Tip: Identify the corpus callosum as the primary commissural pathway facilitating interhemispheric communication in the cerebrum.

 

Question 29. What is meant by brain stem? What are its parts?
Answer: The brain stem is a critical part of the brain located between the spinal cord and the diencephalon (which includes the thalamus and hypothalamus). It controls many vital involuntary functions. Its main parts include:
1. Mid-brain
2. Pons varoli
3. Medulla oblongata
In simple words: The brain stem is a key part of the brain that connects to the spinal cord. It has three main parts: the mid-brain, pons, and medulla oblongata, and it controls important body functions we don't think about, like breathing.

🎯 Exam Tip: Remember the brain stem as the connection between the brain and spinal cord, housing centers for essential life-sustaining functions and listing its three main components.

 

Question 30. What is meant by corpora quadri gemina? What are its functions.
Answer: The corpora quadrigemina are four rounded bumps (papillae) found on the dorsal side of the midbrain. These structures act as reflex centers, primarily involved in the perception of vision and hearing. They help coordinate head and eye movements in response to visual and auditory stimuli.
In simple words: Corpora quadrigemina are four small bumps at the back of the midbrain. They help with quick reactions to things we see and hear, like turning our head when we hear a sound.

🎯 Exam Tip: Associate corpora quadrigemina with reflex centers for vision and hearing, crucial for orienting the body to sensory stimuli.

 

Question 31. What is meant by reflex arc?
Answer: A reflex arc is the neural pathway that mediates a reflex action, which is a fast, involuntary, and unplanned sequence of actions that occurs in response to a particular stimulus. It involves sensory neurons, interneurons (in some cases), and motor neurons working together.
In simple words: A reflex arc is the quick path that an electrical message takes to cause an automatic action, like pulling your hand away from something hot. It doesn't involve your brain thinking about it first.

🎯 Exam Tip: Define reflex arc as the neural pathway for involuntary responses, emphasizing its speed and lack of conscious control.

 

Question 32. What are the functions of cerebellum?
Answer: The cerebellum, located at the back of the brain, is primarily responsible for controlling and coordinating muscular movements. It plays a crucial role in maintaining body equilibrium, posture, and balance. It also fine-tunes motor activities, allowing for smooth and precise movements.
In simple words: The cerebellum helps our body move smoothly, keeps our balance, and makes sure our movements are coordinated and precise.

🎯 Exam Tip: Key functions of the cerebellum are coordination, balance, and fine-tuning voluntary movements, often summarized as the "little brain" for motor control.

 

Question 33. What is meant by receptors?
Answer: Receptors are specialized sensory structures or cells that detect changes occurring in our surrounding environment, both internal and external. When stimulated, they generate nerve impulses that are transmitted to the nervous system for interpretation, making us aware of these changes.
In simple words: Receptors are special parts of our body that sense changes around us, like touch, heat, or light. They send signals to the brain so we know what's happening.

🎯 Exam Tip: Define receptors as sensory structures that detect stimuli and convert them into nerve signals for the brain.

 

Question 34. What is meant by voluntary neural system?
Answer: The voluntary neural system is a part of the peripheral nervous system (PNS) that is associated with the conscious and deliberate control of body movements. It primarily involves the skeletal muscles, allowing us to perform actions like walking, talking, and writing by sending signals from the brain to these muscles.
In simple words: The voluntary neural system is the part of our nervous system that lets us control our body movements on purpose, like when we decide to pick something up.

🎯 Exam Tip: Clarify that the voluntary neural system, also known as the somatic nervous system, governs conscious control over skeletal muscles.

 

Question 35. Name the bacteriocidal substance present in the tears? Where is it seen? Name its secretion?
Answer: Tears contain a bacteriocidal substance called lysozyme enzyme, which helps to destroy bacteria and protect the eyes from infection. Tears are produced and secreted by the lacrimal glands, which are located in the upper lateral region of each orbit. Approximately 1ml of tears is secreted in a day.
In simple words: Tears have an enzyme called lysozyme that kills germs. They come from the lacrimal glands above our eyes, and we make about 1ml of tears each day.

🎯 Exam Tip: Remember lysozyme as the antibacterial agent in tears, secreted by the lacrimal glands for eye protection.

 

Question 36. What are mammillary bodies? What are its functions?
Answer: Mammillary bodies are a pair of small, rounded bodies found within the hypothalamus in the brain. Their main functions include involvement in olfactory reflexes (smell-related reactions) and emotional responses related to odors. They also play a role in memory formation.
In simple words: Mammillary bodies are small, round parts in the brain that help us react to smells and link smells with feelings. They also assist with memory.

🎯 Exam Tip: Connect mammillary bodies to the hypothalamus and their specific roles in olfactory reflexes and emotional memory.

 

Question 37. What are cerebral peduncles?
Answer: Cerebral peduncles are a pair of large, longitudinal bands of nervous tissue that form the lower portion of the midbrain. This region is located between the diencephalon and the pons. They contain various fiber tracts that carry motor and sensory information between the cerebrum and other parts of the nervous system.
In simple words: Cerebral peduncles are two thick bundles of nerve fibers in the midbrain. They carry messages between the top part of the brain and other lower parts.

🎯 Exam Tip: Identify cerebral peduncles as major fiber tracts in the midbrain, essential for communication between higher and lower brain centers.

 

Question 38. What is brain stem? What are its parts?
Answer: The brain stem is a vital part of the brain that connects the cerebrum and cerebellum to the spinal cord. It is located between the spinal cord and the diencephalon. The main parts, or organs, that make up the brain stem are the Mid-brain, Pons, and Medulla oblongata. This structure controls many life-sustaining functions.
In simple words: The brain stem is the connection between the brain and the spinal cord. It has three main parts: the midbrain, pons, and medulla oblongata, and it controls important actions like breathing and heart rate.

🎯 Exam Tip: Remember the brain stem as the central connection point and the site of vital involuntary controls, listing its three main segments.

 

Question 39. What is caudo equina?
Answer: The cauda equina is a thick bundle of elongated nerve roots that appears like a horse's tail. It extends from the end of the spinal cord, specifically after the second lumbar vertebra, and consists of spinal nerves that are greatly elongated to reach their respective destinations.
In simple words: The cauda equina is a group of long nerves at the very bottom of the spinal cord that look like a horse's tail. These nerves carry messages to and from the legs and feet.

🎯 Exam Tip: Visualize the cauda equina as a "horse's tail" of nerve roots, extending beyond the spinal cord proper to innervate lower limbs.

 

Question 40. Where is enlargement region seen in the spinal cord?
Answer: Enlargement regions in the spinal cord are areas where the spinal cord is thicker due to a greater amount of gray matter and larger nerve bundles. These enlargements are seen in two main regions:
- Cervical enlargement
- Lumbar enlargement.
These areas are responsible for innervating the limbs.
In simple words: The spinal cord gets thicker in two places, called the cervical and lumbar enlargements. These thicker parts have more nerves to control the arms and legs.

🎯 Exam Tip: Recall that spinal cord enlargements correlate with innervation of the limbs: cervical for upper limbs and lumbar for lower limbs.

 

Question 41. What is meant by reflex action?
Answer: A reflex action is a rapid, automatic, and involuntary response of the body to a specific stimulus, without conscious thought or control from the brain. When a very quick response is necessary, the spinal cord directly initiates motor actions and brings about an immediate effect. This fast action mediated by the spinal cord is precisely what is called a reflex action.
In simple words: A reflex action is a very fast, automatic body response to something, like pulling your hand away from heat without thinking. The spinal cord handles these quick reactions.

🎯 Exam Tip: Emphasize the involuntary and rapid nature of reflex actions, explaining that the spinal cord often bypasses the brain for quick responses.

 

Question 42. What is meant by peripheral nervous system?
Answer: The Peripheral Nervous System (PNS) includes all the nervous tissue that lies outside of the Central Nervous System (CNS), which comprises the brain and spinal cord. The PNS consists of nerves that extend from the CNS to the rest of the body, including muscles, organs, and sensory receptors, enabling communication between the CNS and the periphery.
In simple words: The Peripheral Nervous System is made of all the nerves outside the brain and spinal cord. It connects the central nervous system to the whole body.

🎯 Exam Tip: Define the PNS as all nerves and neural tissue located outside the brain and spinal cord, linking the CNS to the body's extremities.

 

Question 43. What is meant by mixed nerve?
Answer: A mixed nerve is a type of nerve that contains both afferent (sensory) and efferent (motor) fibers. This means it can carry sensory information from the body to the central nervous system (CNS) and simultaneously transmit motor commands from the CNS to muscles and glands.
In simple words: A mixed nerve is like a two-way street; it carries messages about feelings to the brain and messages for movement from the brain at the same time.

🎯 Exam Tip: Remember that mixed nerves perform a dual function: transmitting both sensory (afferent) and motor (efferent) signals.

 

Question 44. What is meant by pre ganglionic neuron?
Answer: A preganglionic neuron is a neuron whose cell body is located in the brain or spinal cord, within the central nervous system (CNS). Its myelinated axon then exits the CNS as part of a cranial or spinal nerve and travels to an autonomic ganglion, where it synapses with a postganglionic neuron.
In simple words: A preganglionic neuron is a nerve cell whose main body is in the brain or spinal cord. Its fiber leaves the brain or spinal cord and connects to another nerve cell in a special cluster called a ganglion.

🎯 Exam Tip: Emphasize that preganglionic neurons originate in the CNS and project to a ganglion, forming the first part of the autonomic pathway.

 

Question 45. What is autonomic ganglion?
Answer: An autonomic ganglion is a cluster of nerve tissue where the axons of preganglionic neurons synapse with the cell bodies of postganglionic neurons. These ganglia are located outside the central nervous system and are crucial for relaying signals in the autonomic nervous system, which controls involuntary body functions.
In simple words: An autonomic ganglion is like a small station outside the brain and spinal cord where nerve messages are passed from one nerve cell to the next. These messages control things our body does automatically, like breathing or digesting.

🎯 Exam Tip: Understand autonomic ganglia as relay stations in the peripheral nervous system where preganglionic and postganglionic neurons connect for involuntary control.

 

Question 46. What is post ganglionic neuron?
Answer: A postganglionic neuron is a nerve cell that carries electrical signals from an autonomic ganglion to target organs in the body. It acts as a bridge, delivering messages from the central nervous system to the muscles and glands it controls, helping them respond. This neuron helps regulate involuntary body functions like heart rate and digestion.

🎯 Exam Tip: Remember that postganglionic neurons always originate from an autonomic ganglion and transmit impulses to effector organs, completing the autonomic pathway.

 

Question 47. What are the two branches of autonomous nervous system?
Answer: The two main branches of the autonomic nervous system are:
1. Sympathetic neural system
2. Parasympathetic neural system.
Both systems work together, often in opposite ways, to keep the body's internal environment stable, like a balance. Varying distances are called accommodation.

🎯 Exam Tip: Focus on understanding that these two systems typically have opposing effects on organs, like a gas pedal and a brake, to maintain balance.

 

Question 48. Give short notes on Lacrymal glands?
Answer: The lacrimal glands are special glands that make tears. They are also known as tear-secreting glands. Every day, about 1 ml of tears is produced. Tears contain salts, mucus, and an enzyme called lysozyme, which helps kill bacteria and protect the eye from germs.

🎯 Exam Tip: Highlight the three main components of tears-water (for lubrication), lysozyme (for antibacterial action), and salts/mucus (for structure and cleaning).

 

Question 49. What is conjunctiva?
Answer: The conjunctiva is a thin, clear, protective layer that covers the outer surface of the eyeball and the inside of the eyelids. This mucous membrane acts like a shield, keeping the eye moist and protected from tiny particles and infections.

🎯 Exam Tip: Emphasize its protective role and mucous membrane nature, which keeps the eye lubricated and free from external irritants.

 

Question 50. Dilation and congestion of the blood vessels due to local irritation or infections. What is the disease? When will it occur?
Answer: This condition is called Conjunctivitis, often known as "madras eye" or "pink eye." It happens when the blood vessels in the conjunctiva get wide and swollen due to irritation or an infection. This causes the eye to look red and inflamed.

🎯 Exam Tip: Mentioning "madras eye" or "pink eye" is key, and connecting it to inflammation caused by irritation or infection demonstrates full understanding.

 

Question 51. What is sty?
Answer: A sty is a painful, pus-filled lump that forms on the eyelid, usually at the base of an eyelash. It happens when the small ciliary glands around the eyelashes get infected by bacteria, causing a localized swelling. This is a common bacterial infection.

🎯 Exam Tip: Remember a sty is a bacterial infection of a gland in the eyelid, leading to a visible pus-filled bump.

 

Question 52. What are the three types of cell present on the neural retina?
Answer: The neural retina has three main types of cells that help us see:
1. Photoreceptor cells (Rods and Cones)
2. Bipolar cells
3. Ganglion cells.
These cells work together in layers to process light and send visual information to the brain.

🎯 Exam Tip: Listing all three types of cells (photoreceptors, bipolar, ganglion) is crucial for a complete answer, as they form the pathway for visual signal transmission.

 

Question 53. What is cataract?
Answer: Cataract is an eye condition where the clear lens inside the eye becomes cloudy or opaque. This happens due to changes in the proteins that make up the lens. When the lens becomes cloudy, light cannot pass through properly, making vision blurry or hazy.

🎯 Exam Tip: The key idea for cataract is the "opacification of the lens" due to protein changes, leading to blurry vision.

 

Question 54. What is aqueous humour and vitreous humour
Answer:
- Aqueous humour: This is a clear, watery fluid found in the front part of the eye, specifically between the cornea and the iris. It helps nourish the eye structures and maintain eye pressure.
- Vitreous humour: This is a thick, jelly-like substance that fills the large space at the back of the eye, between the lens and the retina. It helps maintain the eye's shape and keeps the retina in place. Both fluids are important for the overall health and function of the eye.

🎯 Exam Tip: Distinguish between aqueous (watery, anterior, nourishes) and vitreous (jelly-like, posterior, maintains shape) humors clearly.

 

Question 55. Give notes on lens fibres?
Answer: The eye lens is a clear, curved structure made of specialized cells called lens fibers. These fibers are long, thin, and columnar in shape. They are composed primarily of crystalline protein, which makes the lens transparent and allows light to pass through for clear vision. These lens fibers are constantly being produced, with older fibers pushed towards the center.

🎯 Exam Tip: Focus on the key characteristics: transparent, biconvex, made of columnar epithelial cells, and crystalline protein composition.

 

Question 56. What are the three layers of eye ball?
Answer: The eyeball is made up of three main layers:
1. Sclera - This is the tough, white outer layer that protects the eye.
2. Choroid - This is the middle layer, which is pigmented and contains many blood vessels to nourish the eye.
3. Retina - This is the innermost layer, which is sensitive to light and contains the cells that detect vision. Each layer has a specific job to help us see.

🎯 Exam Tip: Remember the layers from outer to inner: Sclera (protective white coat), Choroid (pigmented, vascular middle layer), and Retina (light-sensitive inner layer).

 

Question 58. What is meant by maculae lutea?
Answer: The macula lutea is a small, yellowish, flat spot located in the center of the posterior region of the retina. This area is responsible for very sharp and detailed central vision, which we use for tasks like reading and recognizing faces. It contains a high concentration of cone cells.

🎯 Exam Tip: Identify macula lutea as the "yellow spot" and link it directly to "sharp, detailed central vision."

 

Question 59. What is fovea centralis?
Answer: The fovea centralis is a small depression found right in the center of the macula lutea, within the retina. This tiny area contains only cone cells and no rod cells. It provides the sharpest, most focused, and highest-resolution vision. Our eyes naturally move to focus images onto the fovea for detailed viewing.

🎯 Exam Tip: The fovea centralis is the point of sharpest vision due to its high concentration of cones and lack of rods.

 

Question 60. What is blind spot?
Answer: The blind spot is an area on the retina where the optic nerve and retinal blood vessels leave the eye. It is located slightly below the posterior pole. This region does not have any photoreceptors (rods or cones), so it cannot detect light, which is why it's called the "blind spot." Our brain usually fills in this missing visual information.

🎯 Exam Tip: The blind spot is where the optic nerve exits and lacks photoreceptors, causing a gap in vision. This is a common area of confusion with the fovea.

 

Question 61. Why there is no cornea rejection during cornea transplantation?
Answer: During a cornea transplant, there is very little chance of the body rejecting the new cornea. This is because the cornea does not have any blood vessels. Since blood vessels are where immune cells travel, the absence of blood vessels means that immune cells cannot easily reach the transplanted cornea to attack it. This makes it a very successful transplant operation.

🎯 Exam Tip: The key reason for low rejection is the cornea's avascular nature, preventing immune cells from reaching it easily.

 

Question 62. What are the three ear ossicles?
Answer: The three tiny bones in the middle ear, called ear ossicles, help to carry sound vibrations. They are:
1. Malleus - also known as the hammer bone
2. Incus - also known as the anvil bone
3. Stapes - also known as the stirrup bone
These bones work together to amplify sound waves before they reach the inner ear.

🎯 Exam Tip: Remember the common names (hammer, anvil, stirrup) along with their scientific names (Malleus, Incus, Stapes) to ensure you can identify them in any context.

 

Question 63. What are the three chambers of cochlea?
Answer: The cochlea, which is a snail-shaped part of the inner ear, has three main fluid-filled chambers:
1. Scala vestibule
2. Scala tympani
3. Scala media
These chambers contain fluids that move in response to sound vibrations, which helps in the process of hearing.

🎯 Exam Tip: Make sure to list all three scalae correctly: vestibuli, tympani, and media, as they are crucial for sound transmission in the inner ear.

 

Question 64. What is tectorial membrane?
Answer: The tectorial membrane is a stiff, gel-like structure that hangs over the organ of Corti along its entire length, like a roof. It plays an important role in hearing by interacting with the hair cells of the organ of Corti when sound waves cause vibrations, leading to the generation of nerve impulses. This membrane helps in translating mechanical vibrations into electrical signals.

🎯 Exam Tip: The tectorial membrane's key function is its interaction with hair cells in the organ of Corti during sound transduction.

 

Question 65. Name the receptors which are excited by airborne chemicals that dissolve in fluids?
Answer: The receptors that get excited by airborne chemicals dissolving in fluids are called chemoreceptors. These special cells are responsible for our senses of taste and smell. They detect chemical signals in our environment, allowing us to identify different flavors and odors. For example, when you smell food, chemicals from the food dissolve in the mucus in your nose, activating these receptors.

🎯 Exam Tip: Remember that "chemoreceptors" are the general term for receptors responding to chemical stimuli, crucial for taste and smell.

 

Question 66. What is tactile merkel disc?
Answer: A tactile Merkel disc is a specialized cell that acts as a light touch receptor. It is found in the deeper layers of the epidermis, which is the outer skin layer. These discs help us feel steady pressure and light touch, giving us fine detail about textures and shapes we touch. They are especially useful for distinguishing small details on surfaces.

🎯 Exam Tip: Connect Merkel discs to "light touch" and "deeper epidermis" for accurate identification.

 

Question 67. What are the structures present in the membranous labyrinth?
Answer: The membranous labyrinth, located within the bony labyrinth of the inner ear, contains several important structures involved in hearing and balance. These include:
- Cochlea
- Vestibule
- Semicircular canals
These fluid-filled sacs and tubes contain the sensory receptors that convert sound vibrations and head movements into nerve signals. For example, the semicircular canals detect head rotations.

🎯 Exam Tip: Ensure you list all three main components-Cochlea (hearing), Vestibule (static balance), and Semicircular canals (dynamic balance).

 

Question 68. What are the three chambers of cochlea? Name the membrane which separates these chambers?
Answer: The cochlea has three main chambers:
1. Scala vestibuli
2. Scala tympani
3. Scala media
These chambers are separated by specific membranes. The Reissner's membrane separates the scala vestibuli from the scala media. The basilar membrane separates the scala media from the scala tympani. These membranes are crucial for the transmission of sound vibrations within the cochlea.

🎯 Exam Tip: Clearly state all three scalae and the specific membranes that divide them, especially Reissner's and basilar membranes.

 

Question 69. What is meant by stereo cilia?
Answer: Stereo cilia are small, hair-like structures that stick out from the top part of each hair cell found on the basilar membrane in the organ of Corti. These cilia are vital for hearing: when sound waves cause vibrations, the stereo cilia bend, which then generates electrical signals that are sent to the brain, allowing us to perceive sound. They are not true cilia but specialized microvilli.

🎯 Exam Tip: Key points are their location (organ of Corti), hair-like appearance, and role in converting mechanical vibration into electrical signals for hearing.

 

Question 70. What is proprioception?
Answer: Proprioception is our body's ability to sense its own position, orientation, and movement in space. It's like an internal compass that tells us where our body parts are without us having to look. For example, you can touch your nose with your eyes closed because of proprioception. This sense helps us with coordination, balance, and fine motor skills.

🎯 Exam Tip: Define proprioception as the "sense of body position and movement" and give a clear example to illustrate it.

 

Question 71. What is meant by vestibular system?
Answer: The vestibular system is the part of our inner ear responsible for our sense of balance and spatial orientation. It is made up of fluid-filled sacs and tubes, including the utricle, saccule, and semicircular canals. This system continuously sends information to the brain about head movements and position, allowing us to maintain balance and coordinate our eye movements. It helps us know if we are moving, spinning, or tilting our head.

🎯 Exam Tip: Emphasize that the vestibular system is the "organ of balance" and helps detect head position and movement for stable vision and posture.

 

Question 72. Give notes on utriculus and sacculus?
Answer: The utricle and saccule are two small, fluid-filled sacs located in the vestibule of the inner ear. They contain special sensory areas called maculae. These maculae are sensitive to linear movements of the head, such as moving forward, backward, or up and down. They help us sense gravity and know our head's position when we are standing still or moving in a straight line.

🎯 Exam Tip: Highlight that both utricle and saccule contain maculae and are responsible for detecting linear head movements and static head position.

 

Question 73. What is otolith?
Answer: Otoliths are tiny, crystal-like particles, mostly made of calcium carbonate, found within the maculae of the utricle and saccule in the inner ear. They sit on top of the hair cells. When the head moves, these heavier otoliths shift, causing the hair cells to bend. This bending then sends signals to the brain about linear head movements and gravity. They increase the inertia of the sensory membrane, making it more responsive to movement changes.

🎯 Exam Tip: Remember otoliths are calcium carbonate crystals in the maculae that help detect linear acceleration and gravity by their movement against hair cells.

 

Question 74. What are ampullae?
Answer: Ampullae are swollen, bulb-like areas found at one end of each of the semicircular canals in the inner ear. Each ampulla contains a sensory structure called crista ampullaris, which has hair cells and supporting cells. The primary function of the ampullae is to detect rotational movements of the head, like turning your head side to side or nodding. This helps us maintain balance during dynamic movements.

🎯 Exam Tip: Understand that ampullae are the swollen ends of semicircular canals, housing crista ampullaris for detecting rotational head movements.

 

Question 75. Give the name of balancing structures which perform the following action.
a) Linear movement of the head
b) Changes occurring in body position.
c) Rotational movement of the head
Answer:
a) Linear movement of the head: Maculae (in utricle and saccule)
b) Changes occurring in body position: Vestibular system (overall system, including maculae)
c) Rotational movement of the head: Crista ampullaris (in ampullae of semicircular canals)
These structures work together to provide a complete sense of balance and body orientation in space.

🎯 Exam Tip: Clearly differentiate between the maculae (linear movement/gravity) and crista ampullaris (rotational movement).

 

Question 76. What is the unit of sound? Give notes on our ability of sound perception?
Answer: The intensity or loudness of sound is measured in decibels (dB). Our normal hearing range can detect sounds from 0 to 50 dB. However, being exposed to sounds louder than 90 dB for a long time can cause permanent hearing loss. This is why it's important to protect our ears from very loud noises, as our ability to perceive sound can be damaged. Sounds above 90 dB can gradually harm the sensitive hair cells in the cochlea.

🎯 Exam Tip: Remember "decibel" as the unit of sound intensity and the danger threshold of 90 dB for prolonged exposure, which causes hearing loss.

 

Question 77. What are chemo receptors?
Answer: Chemoreceptors are specialized sensory cells that detect chemical stimuli. The receptors for taste and smell are examples of chemoreceptors. These receptors are activated when airborne chemicals (for smell) or chemicals in food (for taste) dissolve in fluids, triggering nerve impulses that the brain interprets as specific odors or flavors. They are crucial for our chemical senses.

🎯 Exam Tip: The main role of chemoreceptors is to respond to chemical signals, linking directly to the senses of taste and smell.

 

Question 78. What are olfactory organs? Where are they situated?
Answer: Olfactory organs are the structures responsible for our sense of smell. These organs are formed by yellowish patches of olfactory epithelium. They are located on the roof of the nasal cavity, high up inside the nose. These cells contain specific receptors that bind to airborne odor molecules, sending signals to the brain for smell identification.

🎯 Exam Tip: Identify olfactory organs as the site for smell and their location on the "roof of the nasal cavity" within the olfactory epithelium.

 

Question 79. What are papillae?
Answer: Papillae are small, raised bumps or projections found on the surface of the tongue. These structures give the tongue its rough texture and are responsible for our sense of taste. Many papillae contain taste buds, which are the actual sensory organs for tasting food. They help grip food and also house the taste receptors.

🎯 Exam Tip: Papillae are the visible projections on the tongue, and they house the taste buds, making them essential for both texture and taste sensation.

 

Question 80. Give notes on taste buds.
Answer: Taste buds are small sensory organs found mainly on the papillae of the tongue, though some are also scattered on the soft palate and cheeks. The cells within taste buds face a lot of wear and tear due to friction from food and hot temperatures. Because of this, they are very dynamic cells and are replaced every seven to ten days. Each taste bud contains taste receptor cells that can detect different flavors like sweet, sour, salty, bitter, and umami.

🎯 Exam Tip: Remember that taste buds are dynamic (rapidly replaced) and contain taste receptor cells, making them essential for chemical detection of flavors.

 

III. Short Answers

 

Question 1. What are the three main functions of nervous system.
Answer: The three main functions of the nervous system are:
1. Sensory functions: It takes in information from both inside and outside the body, like feelings of touch or signals from organs.
2. Motor functions: It sends commands from the brain to muscles and glands, allowing us to move and respond.
3. Autonomic functions: These include reflex actions and involuntary processes, such as breathing and digestion, which happen without us thinking. Together, these functions help the body react to its environment and maintain its internal balance.

🎯 Exam Tip: Categorize the functions into sensory (input), motor (output), and autonomic (involuntary actions/reflexes) for a clear explanation.

 

Question 2. How do we classify neurons on the basis of its functions.
Answer: Neurons can be classified into three main types based on their function:
1. Afferent neurons (Sensory neurons): These neurons carry sensory information from the body's organs and tissues to the central nervous system (CNS). They act like messengers, bringing news from the outside world or inside the body.
2. Efferent neurons (Motor neurons): These neurons carry motor commands from the CNS to effector organs like muscles and glands. They tell the body what to do.
3. Interneurons: These neurons are found entirely within the CNS. They connect afferent and efferent neurons, helping to process information and coordinate responses. They act as the "middlemen" for communication within the brain and spinal cord.

🎯 Exam Tip: Differentiate clearly between afferent (sensory, towards CNS), efferent (motor, away from CNS), and interneurons (within CNS, connecting others).

 

Question 3. What is meant by depolarisation?
Answer: Depolarization is a process where the electrical charge across a neuron's membrane changes. Normally, the inside of the axon membrane is negative, and the outside is positive. During depolarization, sodium ions rush into the cell, making the inside of the axolemma (axon membrane) become positively charged, while the outside becomes negatively charged. This quick reversal of electrical charge is a crucial step in transmitting a nerve impulse. This rapid influx of positive ions is what causes the nerve signal to travel.

🎯 Exam Tip: Key aspects are the influx of sodium ions, the reversal of charge (inside positive, outside negative), and its role as the start of a nerve impulse.

 

Question 4. How is nerve impulses transmitted?
Answer: Nerve impulses are transmitted through a complex electrochemical process. Here's a simplified explanation:
1. At rest, the outside of the axon membrane has a high concentration of sodium ions (Na\(^+\)), and the inside has a high concentration of potassium ions (K\(^+\)) and negatively charged proteins, making the inside negative relative to the outside.
2. When a stimulus reaches a neuron, it causes sodium ion channels to open, allowing Na\(^+\) to rush into the cell. This rapid influx of positive ions reverses the membrane potential, making the inside positive and the outside negative-a process called depolarization.
3. This change in charge creates an action potential, which travels along the axon like a wave. Immediately after depolarization, potassium ion channels open, and K\(^+\) ions rush out of the cell, restoring the negative charge inside and positive outside-a process called repolarization.
4. This whole event, depolarization followed by repolarization, moves along the nerve fiber, allowing the nerve impulse to travel. The image shows how the positive charges of Na\(^+\) outside and negative inside switch during an impulse, moving along the axon, where axolemma is the neuron membrane.
In simple words: A nerve impulse moves when tiny electrical charges switch places along the nerve's outer layer. First, sodium rushes in, making the inside positive. Then potassium rushes out, making it negative again. This quick switch travels like a wave, carrying the message along the nerve.

🎯 Exam Tip: Focus on the movement of sodium (inward) and potassium (outward) ions and the resulting electrical charge changes (depolarization and repolarization) as the core mechanism of impulse transmission.

 

Question 5. What is meant by repolarisation?
Answer: Repolarization is the process where the neuron's membrane quickly returns to its normal resting electrical state after depolarization. This happens when the sodium voltage-gated channels close, stopping the influx of sodium ions. At the same time, potassium voltage-gated channels open, allowing potassium ions (K\(^+\)) to rush out of the cell. This outflow of positive potassium ions lowers the number of positive charges inside the cell, making the inside of the axolemma negative again. This restores the resting potential, getting the neuron ready for another impulse. The repolarization phase is essential for the neuron to reset and transmit new signals.
In simple words: After a nerve signal passes, repolarization is when the nerve cell quickly resets itself. It does this by pushing potassium ions out, making the inside of the cell negative again, ready for the next signal.

🎯 Exam Tip: Key points for repolarization are the closing of sodium channels, opening of potassium channels, and the efflux of K\(^+\) ions to restore the negative internal charge.

 

Question 6. What is meant by hyper polarisation.
Answer: Hyperpolarization occurs when the membrane potential of a neuron becomes even more negative than its normal resting potential, typically dropping from -70 mV to about -90 mV. This happens because the potassium channels, which opened during repolarization, close slowly, allowing extra potassium ions to leave the cell. This makes the inside of the cell overly negative. This state makes it harder for the neuron to fire another action potential immediately, providing a brief recovery period. During hyperpolarization, the K\(^+\) ion gates are more permeable to K\(^+\) even after reaching threshold level; they close slowly, hence called lazy gates. The membrane potential returns to its original resting state when K\(^+\) ion channel closes completely. During hyperpolarization, the Na\(^+\) voltage gate remains closed.
In simple words: Hyperpolarization is when a nerve cell's inside becomes extra negative, even more than usual. This happens because potassium channels close slowly, letting out more positive charges. It makes the cell briefly harder to activate again, like a short rest.

🎯 Exam Tip: Understand hyperpolarization as a temporary state where the membrane potential drops below the resting potential, making the neuron less excitable due to slow-closing potassium channels.

 

Question 7. Give an account of the conduction speed of a nerve impulse.
Answer: The speed at which a nerve impulse travels along an axon depends mainly on two factors. First, if the axon has a larger diameter, the impulse will travel faster. Second, myelinated axons (those covered in a fatty sheath) conduct impulses much faster than non-myelinated axons. This is because the myelin sheath allows the impulse to "jump" along the axon, rather than traveling continuously. This jumping method greatly increases the speed of transmission, allowing for quick responses.
In simple words: How fast a nerve signal moves depends on two things: wider nerves carry signals quicker, and nerves with a special covering (myelin) send signals much faster by making them jump.

🎯 Exam Tip: Remember the two key factors: axon diameter (larger is faster) and myelination (myelinated is much faster due to saltatory conduction).

 

Question 8. What is meant by saltatory conduction?
Answer: Saltatory conduction is a special way nerve impulses travel along myelinated axons, making them very fast. In myelinated axons, the impulse doesn't travel smoothly along the whole nerve. Instead, it "jumps" from one gap in the myelin sheath (called a Node of Ranvier) to the next. The voltage-gated sodium (Na\(^+\)) and potassium (K\(^+\)) channels, which are needed for the impulse, are concentrated only at these nodes. This jumping movement allows the impulse to travel much quicker than in non-myelinated axons, where the impulse has to travel continuously along the entire membrane.
In simple words: Saltatory conduction is like a nerve signal hopping quickly from one uncovered spot to another along a coated nerve fiber. This makes the signal travel much faster than if it had to move along the whole surface.

🎯 Exam Tip: Emphasize "jumping" of impulses between Nodes of Ranvier in myelinated axons, leading to faster conduction, as the core of saltatory conduction.

 

Question 9. Give an account of the membranes (meninges) of brain?
Answer: The brain is protected by three layers of membranes called meninges, which act like protective coverings inside the skull. From outermost to innermost, they are:
1. Duramater: This is the thickest and outermost layer, lining the inner surface of the cranial cavity.
2. Arachnoid mater: This is a thin, web-like middle layer. It is separated from the duramater by a narrow subdural space.
3. Piamater: This is the innermost layer, which is very thin and closely sticks to the surface of the brain. The space between the arachnoid mater and the piamater is called the subarachnoid space, and it contains cerebrospinal fluid. These layers protect the brain from physical shock and infection.

🎯 Exam Tip: List the three meningeal layers in order from outer to inner (Dura, Arachnoid, Pia) and briefly state their key features, especially the location of subarachnoid space.

 

Question 10. List out the functions of brain lobes?
Answer: The brain is divided into several lobes, each with specific functions:
- Frontal Lobe: Involved in behavior, intelligence, memory, and voluntary movement.
- Parietal Lobe: Responsible for language, reading, and processing sensory information like touch, temperature, and pain.
- Temporal Lobe: Plays a role in speech, hearing, and memory.
- Occipital Lobe: Primarily dedicated to visual processing. These lobes work together to perform all the complex functions of the brain.

🎯 Exam Tip: Clearly associate each lobe (Frontal, Parietal, Temporal, Occipital) with its primary functions, such as behavior, sensation, hearing, and vision, respectively.

 

Question 11. Why is thalamus considered as a important relay centre for impulse?
Answer: The thalamus is considered a very important relay center for impulses because it acts like a central switchboard for sensory and motor signals. Almost all sensory information (except smell) coming from the spinal cord and other brain regions first goes to the thalamus. The thalamus then sorts and edits this information before sending it to the correct parts of the cerebrum for further processing. It also plays a key role in learning, memory, and coordinating sensory and motor signals. This ensures that only relevant information reaches the conscious parts of the brain.
In simple words: The thalamus is like a central post office in the brain. It takes all the incoming sensory messages (except smell), sorts them, and sends them to the right places in the brain. This helps with learning and memory too.

🎯 Exam Tip: The critical role of the thalamus is its function as a "relay center" that processes and directs most sensory information (excluding olfaction) to the cerebral cortex.

 

Question 12. Why there may be a death due to the affectation of medulla oblongata?
Answer: Damage to the medulla oblongata can lead to death because this part of the brain controls several essential involuntary functions that keep us alive. The medulla oblongata regulates critical activities such as cardiovascular reflexes (heart rate and blood pressure), respiration (breathing), and gastric secretions (digestion). If this area is affected, the body loses its ability to control these vital functions. For example, if respiration stops, the person cannot breathe, which would cause death. Thus, its proper functioning is crucial for survival.
In simple words: Damage to the medulla oblongata can be deadly because it controls basic body functions like breathing and heart rate. If it stops working, these vital functions also stop, leading to death.

🎯 Exam Tip: The medulla oblongata is a vital center for basic life-sustaining reflexes (cardiovascular, respiratory, gastric), so any damage can be fatal.

 

Question 13. Give notes on mid brain?
Answer: The midbrain is a small but important part of the brain located between the diencephalon and the pons. Its lower portion contains a pair of longitudinal bands of nervous tissue called cerebral peduncles, which act as a relay for impulses between the cerebrum, cerebellum, pons, and medulla. The dorsal (back) part of the midbrain has four rounded bodies known as corpora quadrigemina. These structures act as reflex centers for vision and hearing. The midbrain helps in controlling eye movements and coordinates visual and auditory reflexes.
In simple words: The midbrain is a small part of the brain that connects other parts. It has bundles of nerves that carry signals and also has special areas that control simple seeing and hearing reflexes.

🎯 Exam Tip: Remember the midbrain's location (between diencephalon and pons) and its primary role as a reflex center for vision and hearing through the corpora quadrigemina.

 

Question 14. What are the features we develop when there is a functional deficiency of serotonin and nor epinephrine?
Answer: When there is a lack of serotonin and norepinephrine, which are important brain chemicals (neurotransmitters), people can develop several symptoms of depression. These features include:
- Negative mood: Feeling persistently sad, irritable, or empty.
- Loss of interest: Losing pleasure or interest in activities they once enjoyed.
- Inability to experience pleasure: This is called anhedonia, where one cannot feel joy.
- Suicidal tendencies: In severe cases, thoughts or actions related to self-harm. Antidepressant medications are often used to help treat these symptoms by balancing these brain chemicals.
In simple words: If the brain lacks enough serotonin and norepinephrine, a person might feel very sad, lose interest in things, find it hard to feel happy, and in bad cases, might even think about suicide. These are signs of depression.

🎯 Exam Tip: Associate deficiencies in serotonin and norepinephrine with the core symptoms of depression, especially negative mood, anhedonia, and potential suicidal ideation.

 

Question 15. Give notes on cerebro spinal fluid?
Answer: Cerebrospinal fluid (CSF) is a clear liquid found in the brain and spinal cord. It helps protect the central nervous system and plays several important roles.

• About 150ml of cerebrospinal fluid is present in an adult.
• The body produces approximately 500ml of cerebrospinal fluid daily, and it is replaced every 8 hours.
• The choroid plexus, a network of capillaries in the brain, helps carry harmful waste products from the brain to the blood.

In simple words: Cerebrospinal fluid is a special liquid around your brain and spinal cord. It protects them, carries food, and removes waste. Your body makes about 500ml of it every day, and it's constantly refreshed.

🎯 Exam Tip: Remember the main functions: protection (shock absorber), nourishment, and waste removal. Also, recall the typical volume found in adults and its daily production rate.

 

Question 16. Based on their position how the receptors are classified?
Answer: Receptors are special cells or organs that detect changes in the environment. Based on their location, they are classified into three main types:

1. Exteroceptors: These receptors are located on the body's surface. They help us sense things from the outside world, like hearing, vision, touch, taste, and smell.
2. Interoceptors: These are found inside the body, in organs like the visceral organs and blood vessels. They detect internal stimuli such as blood pressure or oxygen levels.
3. Proprioceptors: These receptors provide information about the body's position and movements. They are located in muscles, tendons, and joints, helping us know where our body parts are without looking.

In simple words: Receptors are classified by where they are in the body. Exteroceptors are on the outside (for sight, touch), interoceptors are inside (for internal body feelings), and proprioceptors tell us about our body's position and movement.

🎯 Exam Tip: Focus on the location and the type of stimuli each category of receptor detects. Provide examples for each to strengthen your answer.

 

Question 17. Your friend is returning home after his visit to USA. All at home are waiting for his arrival. How would you feel? State the division of ANS that predominates and mention few changes take place in your body?
Answer: When a friend returns home after a long time, there would be feelings of excitement and joy. The sympathetic and parasympathetic nervous systems are primarily involved in controlling the body's response to such emotions.

• At first, the sympathetic neural system would be strongly stimulated due to the excitement of seeing the friend. This might lead to an increase in heart rate, faster breathing, and even tears of happiness.
• After some time, as the initial excitement calms down, the parasympathetic neural system will become more active. This helps the body return to a normal, relaxed state, and the secretion of tears might stop. The body always aims to balance these two systems.

In simple words: When your friend arrives, you feel excited, making your heart beat faster and maybe causing happy tears (sympathetic system). Later, you calm down (parasympathetic system), and your body goes back to normal.

🎯 Exam Tip: When describing physiological responses to emotions, clearly differentiate between the "fight or flight" (sympathetic) and "rest and digest" (parasympathetic) functions of the autonomic nervous system.

 

Question 18. What is meant by depression? What are its symptoms?
Answer: Depression is a mood disorder characterized by a persistent feeling of sadness and loss of interest. It is linked to a lack of certain chemicals in the brain, especially serotonin and norepinephrine.
Its symptoms include:

• A pervasive negative mood, meaning feeling down most of the time.
• Loss of interest or pleasure in activities once enjoyed.
• An inability to experience pleasure, also known as anhedonia.
• Suicidal tendencies, which can be a serious risk.

In simple words: Depression is a long-lasting sad feeling where you lose interest in things, often due to low brain chemicals. Symptoms include feeling negative, not enjoying anything, and sometimes thinking about suicide.

🎯 Exam Tip: Clearly define depression as a mood disorder and list its key emotional and behavioral symptoms, especially highlighting the link to neurotransmitter imbalances.

 

Question 19. When dust falls on our eyes like eyelids close immediately not waiting for our willingness, on touching a hot pan the hand is with drawn rapidly. Do you know how this happens?
Answer: These rapid, automatic actions are called reflex actions. They happen without us thinking about them first. When dust falls into the eye or you touch a hot pan, a signal quickly travels from the sensory nerves to the spinal cord. The spinal cord then sends a signal directly back to the muscles to react, causing the eyelids to close or the hand to pull away. This quick response protects the body from harm before the brain even fully processes what happened. This is called a reflex axon or reflex arc, which allows for very fast, involuntary reactions.
In simple words: These are fast, automatic body reactions called reflex actions. When something harmful happens, like dust in your eye or touching heat, your spinal cord quickly tells your muscles to react to protect you, without your brain having to think about it.

🎯 Exam Tip: Emphasize that reflex actions are involuntary, rapid responses that primarily involve the spinal cord, bypassing direct brain processing for speed and protection.

 

Question 20. What are the differences between conditioned and unconditioned reflex.
Answer: Here are the differences between conditioned and unconditioned reflexes:

In simple words: Unconditioned reflexes are natural, inborn reactions, like blinking when something hits your eye. Conditioned reflexes are learned reactions, like your mouth watering when you see food.

🎯 Exam Tip: The key distinction is "inborn" vs. "learned." Use simple, clear examples like blinking (unconditioned) and salivation at the sight of food (conditioned) to illustrate each type.

 

Question 21. What is the difference between exteroceptors and interoceptors.
Answer: Here are the differences between exteroceptors and interoceptors:

In simple words: Exteroceptors sense things outside your body, like touch or sight. Interoceptors sense things inside your body, like how hungry you are or your blood pressure.

🎯 Exam Tip: Focus on the location (surface vs. internal organs) and the source of stimuli (external environment vs. internal body conditions) to distinguish these receptor types.

 

Question 22. Where are lens fiber seen? What is the substance that fills it?
Answer: Lens fibers are found inside the lens of the eye. The lens is a transparent, biconvex structure that helps focus light onto the retina.

• The lens is made up of thin, columnar epithelial cells.
• These specialized cells are called lens fibers.
• Lens fibers are formed from a special protein called crystalline. Crystalline protein makes the lens transparent and flexible, allowing it to change shape for focusing.

In simple words: Lens fibers are inside your eye's lens. They are made of special cells and crystalline protein, which makes the lens clear and helps you focus.

🎯 Exam Tip: Remember that lens fibers are derived from epithelial cells and are primarily composed of crystalline protein, which is essential for the transparency and function of the eye lens.

 

Question 23. What is meant by accommodation of eye? List the structures that are involved in this process?
Answer: Accommodation of the eye refers to its ability to change the focal length of the lens so that objects at varying distances can be focused clearly on the retina. This process allows us to see both near and far objects sharply. To do this, the eye changes the shape of its lens.
This process involves several structures:

• Suspensory ligament: These ligaments hold the lens in place. When they relax or tighten, the lens shape changes.
• Ciliary muscle: This muscle contracts or relaxes to alter the tension in the suspensory ligaments, thereby changing the lens's curvature.
• Ciliary body: This structure contains the ciliary muscle and produces aqueous humor. Its contractions directly affect the shape of the lens.

In simple words: Eye accommodation is how your eye changes its lens shape to see clearly objects that are close or far away. The suspensory ligaments, ciliary muscle, and ciliary body all work together to make this happen.

🎯 Exam Tip: Define accommodation clearly as the eye's ability to adjust lens focus. List and briefly explain the roles of the suspensory ligament, ciliary muscle, and ciliary body.

 

Question 24. Name the structures that helps in fixing eyes in the eye ball?
Answer: The eye is held in its position within the eye socket (orbit of the skull) by six extrinsic muscles. These muscles allow the eye to move in different directions, but they also keep it stable.
The six extrinsic muscles that help fix the eye in the eyeball are:

1. Superior rectus muscle
2. Inferior rectus muscle
3. Lateral rectus muscle
4. Medial rectus muscle
5. Superior oblique muscle
6. Inferior oblique muscle

In simple words: Six special muscles hold your eyeball in place and help it move. They are called superior, inferior, lateral, and medial rectus, and superior and inferior oblique muscles.

🎯 Exam Tip: Remember there are six extrinsic eye muscles. Naming all six rectus and oblique muscles is crucial for a complete answer.

 

Question 25. Name the accessory structure which protects eye?
Answer: The eye is protected by several accessory structures that work together to shield it from harm and keep it healthy. These structures are:

• Eyelashes and Eyebrows: These help protect the eyeballs from foreign objects, sweat, and direct sunlight. Eyebrows also divert sweat from running into the eyes.
• Sebaceous glands or ciliary glands: These glands secrete a lubricating fluid that helps keep the eyelids and eyelashes moist and protected.
• Lacrymal glands: These glands secrete tears. Tears contain salts, mucus, and lysozyme enzyme, which helps to destroy bacteria and keep the eye clean and moist.

In simple words: Your eyes are protected by things like eyelashes, eyebrows (to block dust and sweat), sebaceous glands (for lubrication), and lacrymal glands (which make tears to clean and protect against germs).

🎯 Exam Tip: List the main protective structures and their specific functions (e.g., physical barrier, lubrication, antibacterial action) to demonstrate a full understanding.

 

Question 26. Give an account of aqueous humour?
Answer: Aqueous humor is a clear, watery fluid located in the anterior chamber of the eye, specifically between the cornea and the iris. This fluid is very important for eye health.

• It supplies essential nutrients and oxygen to the avascular structures of the eye, such as the lens and cornea, and also to the retinal cells.
• It is continuously produced by the ciliary body and drained at the same rate, maintaining a balanced flow.
• It maintains a constant intraocular pressure of about 16 mmHg inside the eye, which is vital for keeping the eyeball's shape and for proper vision.

In simple words: Aqueous humor is a clear liquid in the front of your eye. It gives food and oxygen to parts of your eye, keeps the right pressure inside, and is always being made and drained.

🎯 Exam Tip: Highlight the three main functions of aqueous humor: nutrient supply, maintaining intraocular pressure, and its continuous production and drainage cycle. Mentioning its location is also key.

 

Question 27. Give short notes on glaucoma.
Answer: Glaucoma is an eye condition that can lead to blindness if not treated. It happens when the pressure inside the eye (intraocular pressure) becomes too high. This increased pressure damages the optic nerve and the retina, which are crucial for vision. A common cause is a blockage in the canal of Schlemm, which normally drains the aqueous humor fluid from the eye. When this canal is blocked, the fluid builds up, causing the pressure to rise and compress the delicate optic nerve fibers, leading to vision loss over time.
In simple words: Glaucoma is an eye disease caused by too much pressure inside the eye. This high pressure can damage the optic nerve and retina, leading to blindness if not fixed. It often happens when fluid drainage in the eye is blocked.

🎯 Exam Tip: Clearly state that glaucoma involves increased intraocular pressure and subsequent damage to the optic nerve and retina, often due to impaired aqueous humor drainage.

 

Question 28. Name the defects of detraction.
Answer: The question likely refers to "defects of refraction" or "refractive errors" in the eye. These are common vision problems where the eye cannot properly focus light onto the retina, leading to blurry vision. The main types of refractive errors include:

• Myopia (Nearsightedness): Distant objects appear blurry.
• Hypermetropia (Farsightedness): Nearby objects appear blurry.
• Astigmatism: Distorted or blurry vision at all distances due to an irregularly shaped cornea or lens.
• Cataract: The lens of the eye becomes cloudy, leading to blurry vision. (While technically a lens opacity rather than a purely refractive error, it significantly impacts light focusing).

In simple words: "Defects of detraction" most likely means vision problems where the eye can't focus light correctly. These include myopia (can't see far), hypermetropia (can't see near), astigmatism (blurry at all distances), and cataract (cloudy lens).

🎯 Exam Tip: Use the more common term "refractive errors" and list the four primary types: Myopia, Hypermetropia, Astigmatism, and Cataract. Briefly mention how each affects vision.

 

Question 29. Give notes on pigments of colour vision
Answer: Color vision in the human eye is made possible by specialized cells in the retina called cone cells, which contain different light-sensitive pigments. Each pigment is sensitive to a specific range of light wavelengths.

• Red cones: These cones contain a visual pigment called erythropsin. Erythropsin is sensitive to long-wavelength light, particularly in the red region, close to 560 nm.
• Green cones: These cones possess a pigment called chloropsin. Chloropsin is sensitive to medium-wavelength light, primarily in the green region, around 530 nm.
• Blue cones: These cones have a pigment that is sensitive to short-wavelength light, mainly in the blue region, at approximately 420 nm. The interaction and signals from these three types of cones allow the brain to perceive a wide spectrum of colors.

In simple words: Our eyes see colors because of special cells called cones, which have different pigments. Red cones see red light, green cones see green light (using chloropsin), and blue cones see blue light. Together, these help us see all colors.

🎯 Exam Tip: Remember the three types of cone cells (red, green, blue) and their corresponding light-sensitive pigments (erythropsin for red, chloropsin for green). Mentioning the approximate wavelength sensitivity for each will enhance your answer.

 

Question 30. What is the difference between conducting hearing loss and neuro sensory hearing loss.
Answer: Here are the differences between conducting hearing loss and neuro sensory hearing loss:

In simple words: Conducting hearing loss is when sound can't reach the inner ear well, often from blockages or eardrum issues. Neuro sensory hearing loss is when the inner ear or the nerve to the brain is damaged, affecting how sound signals are sent or understood.

🎯 Exam Tip: Clearly differentiate between the *location* of the problem: outer/middle ear for conductive loss and inner ear/auditory nerve/brain for sensorineural loss. Provide common causes for each type.

 

Question 31. Give short notes on melanin.
Answer: Melanin is a natural pigment found in the body, primarily responsible for the color of our skin, hair, and eyes. It is produced by specialized cells called melanocytes.

• Melanocytes are the cells that synthesize melanin.
• Melanin gives color to the skin and also helps protect it from the harmful ultraviolet (UV) rays of the sun. It acts like a natural sunscreen.
• Vitiligo is a condition where melanin pigment is lost from certain areas of the skin, causing white patches to appear.
• Leukoderma occurs when melanocytes fail to produce melanin pigment, leading to similar light or white patches on the skin.

In simple words: Melanin is a color pigment made by melanocytes, giving skin its color and protecting it from the sun. If melanin is lost or not made, it can cause white patches on the skin, as seen in conditions like vitiligo.

🎯 Exam Tip: Define melanin and its origin (melanocytes). Emphasize its dual role in pigmentation and UV protection. Briefly mention related conditions like vitiligo and leukoderma.

 

Question 32. What is meant by the proprioception?
Answer: Proprioception is often called our "sixth sense" because it refers to our body's ability to sense its own position, orientation, and movement in space without looking. It's how we know where our body parts are and how they are moving, even with our eyes closed. For example, you can touch your nose with your finger even if your eyes are closed, thanks to proprioception.

• Our sense of balance is closely related to proprioception, as it helps us maintain stability.
• It is the ability to sense the position, orientation, and movement of the body, allowing for coordinated and precise actions.

In simple words: Proprioception is your body's special sense that tells you where your body parts are and how they are moving, even without looking. It helps you keep your balance and move smoothly.

🎯 Exam Tip: Define proprioception as the body's sense of self-position and movement. Providing a simple example, like touching your nose with eyes closed, effectively illustrates this concept.

 

Question 33. Which is the fastest renewable cells in the body? How is it affected?
Answer: The cells in our taste buds are among the fastest renewing cells in the body. They are replaced very quickly because of their location and constant exposure to various stimuli.

• Taste buds: These small sensory organs on the tongue are constantly exposed to food, heat, and friction.
• Taste bud cells are subjected to huge amounts of friction and are routinely affected by hot foods.
• Due to this constant wear and tear, these are very dynamic cells in the body and are replaced every 7-10 days. This quick renewal ensures that our sense of taste remains sharp.

In simple words: Taste bud cells are the fastest renewing cells in your body. They get damaged often by friction and hot foods, so they are replaced every 7-10 days to keep your sense of taste working well.

🎯 Exam Tip: Identify taste bud cells as fast-renewing cells. Explain that their location and exposure to friction and temperature necessitate rapid replacement for continued function.

 

Question 34. Name the disease which can affect people of any age gender or ethnic group. This is not the contagious disease?
Answer: The disease described is Leucoderma. Leucoderma is a condition where the melanin pigment is lost from certain areas of the skin, resulting in white patches. It is not contagious, meaning it cannot be spread from person to person. This condition can affect individuals of any age, gender, or ethnic background.
In simple words: Leucoderma is a skin condition where melanin, the skin's natural color, is lost, causing white patches. It can affect anyone and is not contagious.

🎯 Exam Tip: Identify Leucoderma by its characteristic white skin patches due to melanin loss and emphasize that it is non-contagious and affects all demographics.

 

Question 35. What are meissner’s corpuscles?
Answer: Meissner's corpuscles are specialized touch receptors found in the skin. They are small, oval-shaped sensory nerve endings that help us detect light touch and subtle pressure changes.

• These are small light pressure receptors located just beneath the epidermis in the dermal papillae, which are ridges in the dermis layer of the skin.
• They are very numerous in hairless skin areas, such as the fingertips, palms of the hands, soles of the feet, and lips. This high concentration in these areas makes them particularly sensitive to fine touch and discriminative sensations.

In simple words: Meissner's corpuscles are tiny sensors in your skin that help you feel light touch and small pressure changes. You have many of them in sensitive, hairless areas like your fingertips.

🎯 Exam Tip: Describe Meissner's corpuscles as light touch receptors located in the dermal papillae of hairless skin, important for discriminating fine textures.

 

IV. Brief Answers

 

Question 1. Describe structure of a neuron.
Answer: A neuron, also known as a nerve cell, is the basic functional unit of the nervous system. It is designed to transmit electrical and chemical signals. A neuron is composed of three main regions:

1. Cell body (Soma): This is the main part of the neuron, spherical in shape. It contains the nucleus, which lacks a centriole (meaning mature neurons generally do not divide). It also has cytoplasm filled with Nissl's granules, which are involved in protein synthesis. The plasma membrane covering the neuron is called the neurilemma.
2. Dendrites: These are short, repeatedly branched fibers that extend from the cell body. Dendrites receive incoming nerve impulses from other neurons and transmit them towards the cell body. Nissl's granules are also present in the cytoplasm of dendrites.
3. Axon: This is a single, long fiber that extends from a cone-shaped area of the cell body called the axon hillock. Unlike the cell body and dendrites, the axon typically lacks Golgi bodies and Nissl's granules in its cytoplasm.
   • The axon of peripheral nerves is often surrounded by Schwann's cells, which form a fatty layer called the myelin sheath.
   • The myelin sheath is not continuous; there are small gaps along its length called Nodes of Ranvier, which help speed up impulse conduction.
   • At its distal end, the axon branches into many fine terminals, each ending in a knob-like structure called a synaptic knob.
   • Synaptic knobs contain synaptic vesicles, which are small sacs filled with chemical messengers called neurotransmitters.
   • The axon's primary function is to transmit nerve impulses away from the cell body towards other neurons or effector organs (like muscles or glands). Myelinated nerve cells transmit impulses much faster than non-myelinated ones. The plasma membrane covering the axon is called the axolemma.

In simple words: A neuron has three main parts: the cell body (with the nucleus), dendrites (which receive signals), and a long axon (which sends signals). The axon is often covered in a myelin sheath with gaps, helping signals travel fast. The end of the axon has synaptic knobs that release chemical messages.

🎯 Exam Tip: Clearly delineate the three main parts of a neuron and describe the function and key features of each. Mentioning the presence or absence of Nissl's granules and the role of the myelin sheath and Nodes of Ranvier are important details.

 

Question 2. Describe about the different types of neuron with diagram?
Answer: Neurons are classified into different types based on the number of processes (axon and dendrites) extending from their cell body. Here are the main types:

1. Multipolar neurons: These neurons have many processes. Typically, they have one axon and two or more dendrites extending from the cell body. They are the most common type of neuron in the central nervous system, such as in the brain and spinal cord.
2. Bipolar neurons: These neurons have two processes. They possess one axon and one dendrite, both extending from opposite ends of the cell body. Bipolar neurons are found in specialized sensory organs, such as the retina of the eye, the inner ear, and the olfactory area of the brain.
3. Unipolar neurons: These neurons have a single short process that extends from the cell body. This single process then branches into an axon and a dendrite. Unipolar neurons are typically found in the sensory ganglia of the peripheral nervous system.

In simple words: Neurons are grouped by how many extensions they have. Multipolar neurons have many branches (most common). Bipolar neurons have two branches (found in eyes and ears). Unipolar neurons have one branch that splits (found in sensory nerves).

🎯 Exam Tip: When asked to describe different neuron types, clearly state the number of processes for each and provide specific examples of where they are found in the body. A simple sketch highlighting these structural differences is highly recommended.

 

Question 3. Give an account of Ionic channels in the axolemma?
Answer: The axolemma, which is the plasma membrane of the axon, contains specialized protein channels called ionic channels. These channels are crucial for the generation and transmission of nerve impulses by controlling the movement of ions across the membrane. There are three main types of ionic channels:

1. Leakage channels:
   • These channels are always open, allowing ions to "leak" across the membrane continuously.
   • Potassium (K\(^+\)) leakage channels are more numerous and allow more K\(^+\) ions to leak out compared to sodium (Na\(^+\)) leakage channels, which allow Na\(^+\) ions to leak in.
   • The axolemma has a greater permeability to K\(^+\) ions than to Na\(^+\) ions.
   • The continuous movement of these ions helps maintain the resting membrane potential, which is the electrical potential difference across the axolemma when the neuron is not actively transmitting a signal.
2. Ligand-gated channels:
   • These are chemically gated channels, meaning they open or close in response to the binding of a specific chemical messenger, called a ligand (e.g., a neurotransmitter).
   • They are found in the postsynaptic membrane at synapses. When neurotransmitters bind to them, they cause a change in the membrane potential of the postsynaptic neuron. For instance, acetylcholine can open these channels, allowing Na\(^+\) and Ca\(^{++}\) ions to diffuse inward and K\(^+\) ions to diffuse outward, initiating a new signal.
3. Voltage-gated channels:
   • These channels open or close in response to changes in the electrical potential (voltage) across the membrane.
   • They are essential for generating and propagating action potentials. When the membrane potential reaches a certain threshold, these channels rapidly open.
   • There are specific sodium voltage-gated channels and potassium voltage-gated channels that operate during depolarization and repolarization phases of an action potential.

In simple words: Ionic channels in the axon's membrane control how ions move, which is key for nerve signals. Leakage channels are always open, keeping the resting charge. Ligand-gated channels open when a chemical attaches to them, like a key in a lock. Voltage-gated channels open when the electrical charge across the membrane changes, helping send fast signals.

🎯 Exam Tip: For ionic channels, remember the three types: leakage (always open, maintaining resting potential), ligand-gated (chemically controlled, at synapses), and voltage-gated (electrically controlled, for action potentials). Illustrate with ion movements.

 

Question 4. Give an account of resting potential?
Answer: The resting potential is the electrical potential difference that exists across the plasma membrane of a neuron when it is not actively transmitting a nerve impulse. In a resting neuron, the inside of the cell is negatively charged relative to the outside. Its normal value is typically around -70mV, though it can range from 40mV to 90mV.

• The electrical potential difference across the plasma membrane of a resting neuron is called the resting potential.
• More potassium (K\(^+\)) ions tend to leak out of the neurilemma than sodium (Na\(^+\)) ions leak into it, largely due to a higher number of K\(^+\) leakage channels.
• Because more positive ions leave the cell than enter, the interior of the cell becomes negative.
• In the resting state, the axon membrane is more permeable to K\(^+\) and less permeable to Na\(^+\) ions. It is almost impermeable to negatively charged protein ions found inside the cell.
• Outside the axon, there is a high concentration of Na\(^+\) ions and a low concentration of K\(^+\) ions. This concentration difference is crucial.
• This difference in ion concentration is actively maintained by the ATP-driven sodium-potassium pump, which exchanges three Na\(^+\) ions outwards for two K\(^+\) ions inwards. This pump is vital for re-establishing the resting potential after a nerve impulse.

In simple words: Resting potential is the electrical charge difference across a nerve cell's membrane when it's quiet. The inside is negative (around -70mV) because more potassium leaks out than sodium comes in, and a special pump works to keep this balance by moving ions.

🎯 Exam Tip: Define resting potential as the electrical difference across a non-firing neuron membrane. Explain the role of differential ion permeability (more K\(^+\) exit, less Na\(^+\) entry) and the active Na\(^+\)-K\(^+\) pump in maintaining this negative internal charge.

 

Question 5. a) What is meant by action – membrane potential? b) What is Depolarisation?
Answer:
a) Action - Membrane Potential: An action potential is a rapid, temporary change in the electrical potential across the membrane of a neuron, moving from a negative resting state to a positive state and then back to negative. It is the electrical signal that a neuron uses to send information along its axon, away from the cell body. This "all-or-none" event is crucial for nerve impulse transmission.
b) Depolarization: Depolarization is the first phase of an action potential. It occurs when a nerve fiber is stimulated, causing voltage-gated sodium (Na\(^+\)) channels to open rapidly. This allows a large influx of Na\(^+\) ions from outside to inside the axolemma. As these positive Na\(^+\) ions rush in, the inside of the axolemma becomes positively charged, and the outside becomes negatively charged, reversing the normal resting potential. This reversal of electrical charge is what is called depolarization. The membrane potential shoots up to approximately +45mV during this phase, creating the "spike potential." The influx of Na\(^+\) must reach a certain level (threshold potential, around -55mV) to trigger the full action potential.
In simple words: a) Action potential is a quick electrical signal that nerves use to send messages. The nerve's electrical charge quickly changes from negative to positive and back. b) Depolarization is when the nerve cell's inside becomes positive as sodium ions rush in, making the electrical signal start. This happens if the signal reaches a certain strength, called the threshold.

🎯 Exam Tip: For action potential, emphasize its "all-or-none" nature and its role in information transmission. For depolarization, focus on the rapid influx of Na\(^+\) ions through voltage-gated channels, which reverses the membrane potential from negative to positive.

 

Question 6. What is synapsis?
Answer: A synapse is a specialized junction where two neurons communicate with each other, or where a neuron communicates with an effector cell (like a muscle or gland cell). It's where a nerve impulse is transmitted from one cell to another. Synapses are essential for the flow of information throughout the nervous system.

• The junction between two neurons is called a synapse, and it's how nerve impulses are transmitted.
• The first neuron involved in the synapse is called the presynaptic neuron, which sends the signal. The second neuron, which receives the signal, is called the postsynaptic neuron.
• There is a small gap between these two neurons called the synaptic cleft. Signals cross this gap.
• The axon terminals of the presynaptic neuron contain synaptic vesicles, which are tiny sacs filled with chemical messengers called neurotransmitters.
• When an electrical impulse arrives at the axon terminal, it causes the presynaptic membrane to depolarize. This depolarization opens voltage-gated calcium channels.
• 
  \( \implies \) The influx of calcium ions into the presynaptic terminal stimulates the synaptic vesicles to move towards the presynaptic membrane and fuse with it.
• 
  \( \implies \) When the vesicles fuse, they release their neurotransmitters into the synaptic cleft through a process called exocytosis.
• The released neurotransmitters then diffuse across the synaptic cleft and bind to specific receptors located on the postsynaptic membrane.
• 
  \( \implies \) This binding of neurotransmitters to receptors can generate a new electrical potential (a graded potential) in the postsynaptic neuron.
• This new potential can be either excitatory (causing depolarization and making the postsynaptic neuron more likely to fire an action potential) or inhibitory (causing hyperpolarization and making it less likely to fire).

In simple words: A synapse is the tiny connection point where two nerve cells talk to each other. One cell sends chemical messages (neurotransmitters) across a small gap, and the other cell receives them, either getting excited to send its own message or told to stay quiet.

🎯 Exam Tip: Define a synapse as the point of communication between neurons. Clearly identify the presynaptic neuron, postsynaptic neuron, synaptic cleft, and the role of neurotransmitters in signal transmission via vesicles and receptors.

 

Question 8. Describe the structure of human brain with a diagram?
Answer: The human brain is protected inside the skull within the cranial cavity. It is covered by three protective membranes called cranial meninges. The outermost layer is the dura mater, the middle thin layer is the arachnoid mater, and the innermost layer that adheres to the brain surface is the pia mater. These layers provide important protection and support to the brain. The brain itself is divided into three main regions: the forebrain, midbrain, and hindbrain.
The cerebrum and diencephalon make up the forebrain. The cerebral cortex has grey matter made of unmyelinated nerve cells, and white matter. The surface has many folds called gyri and shallow grooves called sulci. These help to increase the surface area. The cerebrum has eight lobes: pairs of frontal, parietal, temporal, and occipital lobes. The brain is divided into two hemispheres by a longitudinal fissure, connected by a nerve tract called the corpus callosum. The cerebral cortex has three main functional areas:

• Sensory areas: These are found in the parietal, temporal, and occipital lobes of the cortex, where sensory information is processed.
• Motor areas: These areas are located in the posterior part of the frontal lobes and control voluntary muscle movements.
• Association area: This area is between the cortex and diencephalon and is involved in memory, communication, learning, and reasoning. These areas help us to perform complex functions like thinking and problem-solving.

In simple words: The brain is protected by membranes and divided into several parts, each with its own job. It's like a control center that makes us think, feel, and move. The cerebrum handles thinking and movement, with special areas for different tasks.

🎯 Exam Tip: When describing the brain, always mention its protective layers (meninges) and the major divisions, highlighting the functions of the cerebral cortex lobes.

 

Question 9. Describe the structure of hind brain?
Answer: The hindbrain is also known as the rhombencephalon. It consists of three main parts: the cerebellum, pons varolii, and medulla oblongata.
Cerebellum: This is the second largest part of the brain. It has two cerebellar hemispheres and a central worm-shaped part called the vermis.
Function: The cerebellum is essential for controlling and coordinating muscular movements and maintaining body balance. If the cerebellum is damaged, it can lead to uncoordinated voluntary muscle movements.
Pons varolii: This part is located between the midbrain and the medulla oblongata. It forms a bridge that connects the two cerebellar hemispheres and links the medulla oblongata with other brain regions.
Medulla oblongata: This is the most posterior part of the brain. It connects the spinal cord with various other brain parts. It receives and processes signals from the spinal cord and sends them to the cerebellum and thalamus.
Function: The medulla oblongata is crucial for controlling vital involuntary functions like cardiovascular reflexes, respiration (breathing), and gastric secretions. Damage to this area can be life-threatening.In simple words: The hindbrain is at the back of your head and helps with balance, coordination, and important body functions like breathing. It has three main parts: cerebellum for movement, pons for connecting parts, and medulla for vital actions.

🎯 Exam Tip: Focus on the three main components of the hindbrain (cerebellum, pons, medulla oblongata) and remember at least one key function for each to score well.

 

Question 10. Describe the structures of diencephalon?
Answer: The diencephalon is a vital part of the forebrain that sits between the cerebrum and the midbrain. It is made up of three main structures: the epithalamus, thalamus, and hypothalamus, each with specific roles.
Epithalamus:

• This is not nervous tissue but a short stalk that ends in a small, rounded structure called the pineal body.
• The anterior part of the epithalamus is rich in blood vessels and forms the anterior choroid plexus.
• The pineal body secretes the hormone melatonin, which helps regulate the body's sleep-wake cycle.

Thalamus:

• The thalamus is primarily made of grey matter.
• It acts as a crucial relay center, receiving impulses from the spinal cord, brain stem, and other parts of the brain, and then sending them to the cerebrum.
• It plays a key role in learning and memory, helping to sort and edit information before it reaches the cerebral cortex.
• It is also a major coordinating center for sensory and motor signals, ensuring information is sent to the correct areas.

Hypothalamus:

• This forms the floor of the diencephalon.
• It contains a pair of small, rounded structures called mammillary bodies, which are involved in olfactory reflexes and emotional responses related to smell.
• The hypothalamus is essential for maintaining homeostasis (internal balance) in the body. For example, it controls body temperature and regulates feelings of hunger and thirst. It also contains neurosecretory cells that produce hypothalamic hormones and acts as the satiety center, helping to control appetite.

In simple words: The diencephalon is like a central hub in the brain. It includes the epithalamus (for sleep), thalamus (for sorting messages), and hypothalamus (for body balance, hunger, thirst, and emotions).

🎯 Exam Tip: Remember the three parts of the diencephalon and associate one main function with each to provide a comprehensive answer.

 

Question 11. Give an account of ventricles of the brain.
Answer: The brain contains four hollow, fluid-filled spaces called ventricles. These ventricles are important for producing and circulating cerebrospinal fluid (CSF), which protects the brain.

• The first and second lateral ventricles are C-shaped spaces found inside each cerebral hemisphere. They are separated by a thin membrane called the septum pellucidum.
• Each lateral ventricle connects with the third ventricle through an opening known as the foramen of Monro.
• The third ventricle then opens into the fourth ventricle through a canal called the aqueduct of Sylvius.
• The choroid plexus, a network of blood capillaries located in the root of the ventricles, produces the cerebrospinal fluid. This fluid is crucial for the brain's health.

Functions of Cerebrospinal Fluid (CSF):

• CSF provides buoyancy to the Central Nervous System (CNS), helping the brain float and reducing its effective weight.
• It acts as a shock absorber, protecting the brain from physical impacts.
• It nourishes the brain cells by delivering food and oxygen.
• It carries harmful metabolic wastes away from the brain to the blood, ensuring a clean environment.
• It helps maintain constant pressure inside the cranial vessels.

In simple words: The brain has four spaces called ventricles filled with special fluid (CSF). This fluid helps the brain float, protects it from bumps, brings it food and oxygen, takes away waste, and keeps the pressure inside the head stable.

🎯 Exam Tip: Highlight the role of CSF in protection, nourishment, and waste removal, and know the names of the main ventricles and their connections.

 

Question 12. Differentiate the conditioned stimulus from unconditioned stimulus.
Answer: The differences between conditioned and unconditioned stimuli relate to how an organism learns and responds to its environment. Conditioned stimuli are learned, while unconditioned stimuli are natural.

In simple words: Unconditioned reflexes are things you do naturally without thinking, like blinking when something comes near your eye. Conditioned reflexes are things you learn to do, like getting excited when you see food.

🎯 Exam Tip: Clearly state whether the reflex is inborn or learned and provide a distinct, simple example for each type.

 

Question 13. Tabulate the nerves and functions and its nature of 6-12th cranial nerves.
Answer: Cranial nerves are nerves that emerge directly from the brain, as opposed to the spinal cord. There are 12 pairs of cranial nerves, each with specific functions and characteristics (sensory, motor, or mixed).

In simple words: Cranial nerves are like special wires directly from your brain, each with a specific job. Some help you smell, see, or hear, while others control your eye movements, face muscles, or even organs inside your body.

🎯 Exam Tip: Practice listing the cranial nerves by their Roman numeral, name, and primary function. This is a common question in anatomy exams.

 

Question 14. Tabulate the functions of sympathetic and parasympathetic nerve.
Answer: The autonomic nervous system has two main parts, the sympathetic and parasympathetic nervous systems, which often have opposite effects to keep the body in balance. The sympathetic system prepares the body for "fight or flight," while the parasympathetic system handles "rest and digest."

In simple words: The sympathetic system gets your body ready for action (like running or fighting), making your heart beat faster and pupils bigger. The parasympathetic system helps your body calm down and rest, like when you are digesting food.

🎯 Exam Tip: Understand that these two systems typically have opposing effects on organs, helping to maintain balance within the body. Remember "fight or flight" for sympathetic and "rest and digest" for parasympathetic.

 

Question 15. Describe the structure of cross section of spinal cord.
Answer: A cross-section of the spinal cord reveals its internal organization, which is crucial for transmitting signals between the brain and the rest of the body. It consists of both grey and white matter arranged in specific patterns.

• The spinal cord has two indentations: the posterior median sulcus at the back and the anterior median fissure at the front.
• Inside, the grey matter forms an H- or butterfly-shaped region, which is surrounded by the outer white matter.
• The grey matter mainly contains dendrites, interneurons, and glial cells. It is organized into different horns:
  • Dorsal horn: Contains cell bodies of interneurons, which receive sensory information.
  • Ventral horn: Contains efferent motor neurons that supply skeletal muscles, initiating movement.
  • Lateral horn: Contains nerves that supply the heart, smooth muscles, and exocrine glands. These neurons originate from the cell bodies here.
• The white matter consists of bundles of nerve fibers, organized into tracts:
  • Ascending tract: These tracts carry sensory impulses upwards to the brain.
  • Descending tract: These tracts carry motor impulses downwards from the brain to the body.

In simple words: The spinal cord is like a main cable that connects your brain to your body. It has a butterfly-shaped grey part inside for processing signals and a white outer part for sending signals up and down, like highways.

🎯 Exam Tip: When drawing or describing the spinal cord, always identify the grey matter (H-shape), white matter, central canal, and the dorsal/ventral nerve roots for full marks.

 

Question 16. Give an account of the functional components of a reflex arc.
Answer: A reflex arc is the neural pathway that controls a reflex, allowing for a rapid, involuntary response to a stimulus without involving the brain directly at first. It typically involves five main components working in sequence:

• Sensory Receptor: This is a specialized structure, often in the skin or an organ, that detects a specific stimulus, such as heat, pressure, or pain.
• Sensory Neuron (Afferent Neuron): This neuron carries the sensory impulse from the receptor to the central nervous system (CNS). It enters the spinal cord through the dorsal root.
• Interneuron (Relay Neuron): Located within the CNS (usually the spinal cord), this neuron connects the sensory neuron to the motor neuron. It processes the signal and decides on the appropriate response.
• Motor Neuron (Efferent Neuron): This neuron transmits the impulse from the CNS to the effector organ, carrying the command for action.
• Effector Organ: This is typically a muscle or a gland that responds to the motor impulse by contracting (muscle) or secreting (gland). This rapid action helps to protect the body from harm.

In simple words: A reflex arc is like a quick pathway for messages in your body. It has a sensor (receptor), a message carrier to the brain (sensory neuron), a connection in the brain (interneuron), a message carrier from the brain (motor neuron), and a responder (effector organ) that acts fast without you even thinking.

🎯 Exam Tip: Remember the five components in order: receptor, sensory neuron, interneuron, motor neuron, and effector. This sequence is key to understanding how reflexes work.

 

Question 17. Tabulate the differences between sympathetic and parasympathetic neural system.
Answer: The sympathetic and parasympathetic neural systems are two divisions of the autonomic nervous system that work together to regulate involuntary body functions. They often have opposing effects to maintain bodily balance.

In simple words: The sympathetic system gets your body ready for action from the middle of your spine, while the parasympathetic system calms you down from your brain and lower spine. They use different chemicals and have opposite effects.

🎯 Exam Tip: Focus on the origin, length of fibers, primary neurotransmitters, and the general "fight or flight" vs. "rest and digest" roles to differentiate these two systems effectively.

 

Question 18. Give an account of peripheral nervous system.
Answer: The peripheral nervous system (PNS) includes all the nervous tissue located outside the central nervous system (CNS), which means everything beyond the brain and spinal cord. It plays a crucial role in connecting the CNS to the limbs and organs, acting as a communication network.

• The PNS includes nerves, ganglia (clusters of nerve cell bodies), enteric plexuses (networks of nerves in the digestive system), and sensory receptors.
• Ganglia are masses of nervous tissue that often contain the cell bodies of neurons.
• The neurons in the enteric plexuses help regulate the digestive system's functions.
• Specialized structures called sensory receptors detect changes in the environment, both internal and external. These receptors trigger nerve impulses that travel along afferent fibers towards the CNS.
• The PNS is composed of 12 pairs of cranial nerves, which originate from the brain, and 31 pairs of spinal nerves, which emerge from the spinal cord.
• The neural retina layer within the eye, which detects light, consists of specialized cells called cones and rods.
• The macula lutea is a yellow flat spot at the center of the posterior region of the retina, responsible for sharp, detailed vision. A small depression within this macula is the fovea centralis, which contains only cones and provides the clearest vision.

In simple words: The peripheral nervous system is all the nerves and sensors outside your brain and spinal cord. It carries messages to and from your brain, helping you feel things, move your body, and control internal organs.

🎯 Exam Tip: Remember that the PNS connects the CNS to the rest of the body, includes cranial and spinal nerves, and has sensory receptors for external and internal stimuli.

 

Question 19. Describe the structure of an eye.
Answer: The eye is a complex sensory organ responsible for vision, located in the orbit of the skull. It is held in place and controlled by six extrinsic muscles. Several accessory structures protect the eye:

• Eyelashes and Eyebrows: These protect the eyeballs from foreign objects, sweat, and direct sunlight.
• Glands: Sebaceous (oil) glands or ciliary glands secrete a lubricating fluid. Lacrymal glands secrete tears, which contain salts, mucus, and lysozyme enzymes to destroy bacteria and keep the eye clean and moist.

The eyeball itself has three main layers and two fluid-filled compartments:
Layers of the Eyeball:

• Sclera (Outer Coat): This is the outermost protective layer, forming the white of the eye. Anteriorly, it becomes the transparent cornea. The cornea is made of stratified squamous epithelium. At the junction of the sclera and cornea, there is a channel called the canal of Schlemm, which drains excess aqueous humor.
• Choroid (Pigmented Middle Layer): This layer is highly vascularized and pigmented. Anteriorly, the choroid thickens to form the ciliary body and the colored part called the iris.
• Retina (Inner Most Layer): This neural layer contains photoreceptor cells (rods and cones) that detect light. It has two main regions:
  • A sheet of non-visual pigmented part.
  • A neural visual region.

Other Key Structures:

• Lens: A transparent, biconvex structure made of long columnar epithelial cells called lens fibers, which are formed of crystalline protein. It focuses light onto the retina.
• Pupil: The aperture at the center of the iris through which light enters the eye.

Fluid-filled Compartments:

• Aqueous Humor: A fluid that fills the anterior compartment, located between the cornea and the iris.
• Vitreous Humor: A jelly-like fluid that fills the posterior compartment, located between the lens and the retina.

Vision Accommodation: The ability of the eyes to focus objects at varying distances is called accommodation, achieved by the suspensory ligament and ciliary muscle working together.In simple words: Your eye is like a camera. It has outer protective parts like eyelids and tears. Inside, there are three layers: the outer white part (sclera) with a clear front (cornea), a middle colored part (choroid) with the iris, and an inner layer (retina) that sees light. There's also a lens to focus and liquids to keep it healthy.

🎯 Exam Tip: Remember the three main layers of the eye (sclera, choroid, retina), the two fluid-filled compartments (aqueous and vitreous humor), and the key role of the lens and pupil.

 

Question 20. Draw the diagram of cross section of the eye.
Answer: Here is a diagram showing the cross-section of the human eye, illustrating its various parts and their relative positions.In simple words: This diagram shows how the eye is shaped like a ball, with a clear front window (cornea), a lens inside to focus light, and nerves at the back to send messages to the brain. Liquids inside help keep its shape and health.

🎯 Exam Tip: When drawing or interpreting eye diagrams, clearly label the cornea, lens, retina, optic nerve, and the two humors (aqueous and vitreous) as these are central to eye function.

 

Question 21. Describe about the mechanism of vision.
Answer: The process of vision involves several steps, starting with light entering the eye and ending with the brain interpreting images. It’s a complex conversion of light energy into electrical signals.

1. When light enters the eye, it first passes through the cornea, then the aqueous humor, and finally the lens. These structures refract (bend) the light.
2. The refracted light is focused onto the retina, which contains specialized photoreceptor cells called rods and cones.
3. Rods and cones contain light-sensitive pigments. Rods contain retinal (a derivative of vitamin A) and the photopigment opsin, which combine to form rhodopsin. Cones contain retinal and different opsin proteins, which combine to form photopsin.
4. Light causes the photopigments to break down (dissociate) into retinal and opsin, leading to structural changes in the opsin molecule.
5. These structural changes generate an action potential (an electrical signal) in the photoreceptor cells.
6. This electrical signal is then transmitted from the photoreceptor cells to bipolar cells, then to ganglion cells, and finally, via the optic nerves, to the visual cortex of the brain.
7. The visual cortex interprets these signals as images, allowing us to perceive what we see. This entire pathway ensures that light information is precisely converted into visual perception.

In simple words: When you look at something, light goes into your eye and hits the back part called the retina. Special cells in the retina turn the light into electrical signals. These signals then travel through nerves to your brain, which figures out what you are seeing.

🎯 Exam Tip: Remember the pathway of light through the eye (cornea, lens, retina) and the conversion of light into electrical signals by photoreceptors before transmission to the brain via the optic nerve.

 

Question 22. List the refractive errors of eye.
Answer: Refractive errors occur when the eye cannot properly focus light onto the retina, leading to blurred vision. These conditions can often be corrected with lenses or surgery.
Myopia (Nearsightedness):

• A person with myopia can see nearby objects clearly but has difficulty seeing distant objects.
• This occurs when the eyeball is elongated, or the lens is too thick, causing the image of distant objects to form in front of the retina.
• This error can be corrected by using a concave lens, which diverges light rays before they enter the eye, pushing the focal point back onto the retina.

Hypermetropia (Farsightedness):

• An affected person cannot see nearby objects clearly.
• This condition is due to a shortened eyeball or a thin lens, causing the image of close objects to focus behind the retina.
• This defect can be corrected by using a convex lens, which converges light rays before they enter the eye, moving the focal point forward onto the retina.

Presbyopia:

• This occurs due to aging, where the eye lens loses its elasticity and ability to accommodate (change focus).
• It is corrected with convex lenses.

Astigmatism:

• This defect results from an irregular curvature of the cornea or lens.
• It is corrected using cylindrical glasses.

In simple words: Refractive errors are problems with how your eye focuses light. Myopia means you see near things clearly but far things are blurry, fixed with a concave lens. Hypermetropia means far things are clear but near things are blurry, fixed with a convex lens. Presbyopia is age-related focusing trouble, and astigmatism is uneven vision due to an uneven eye surface.

🎯 Exam Tip: For each refractive error, clearly state the visual problem, the underlying cause in the eye, and the type of lens used for correction.

 

Question 23. Describe the structure of an ear?
Answer: The ear is divided into three main parts: the external ear, the middle ear, and the inner ear. Each part has specific structures that help us hear. The external ear collects sound, the middle ear amplifies it, and the inner ear converts it into signals for the brain.
External Ear:
It includes the pinna (the visible part of the ear), the external auditory meatus (ear canal), and the eardrum (tympanic membrane). The pinna collects sound waves, which then travel through the ear canal to the eardrum. The tympanic membrane is covered by skin on the outside and mucus membrane on the inside.
Middle Ear:
This is an air-filled space within the temporal bone. It holds three small bones called ossicles: malleus, incus, and stapes. The malleus is connected to the eardrum, and its head joins the incus. The stapes is connected to the oval window, which leads to the inner ear. The Eustachian tube connects the middle ear cavity to the pharynx.
Inner Ear:
This fluid-filled part contains two main structures: the bony labyrinth and the membranous labyrinth. The bony labyrinth has three areas: the cochlea, vestibule, and semicircular canals. The cochlea is a coiled part with three chambers: Scala vestibule, Scala media, and Scala tympani. The scala vestibule and scala tympani are filled with perilymph, while the scala media contains endolymph.
In simple words: The ear has three parts: outer, middle, and inner. The outer part gathers sound, the middle part has tiny bones to make sounds louder, and the inner part turns sounds into brain signals, which helps us hear.

🎯 Exam Tip: When describing a biological structure, always break it down into its main parts and then describe each part's components and their functions clearly.

 

Question 24. Describe the structure and functions of organ of cortii.
(A diagram of the inner ear showing the organ of corti with labels like tectorial membrane, basilar membrane, hair cells, etc., is present here in the source content.)
Answer: The organ of Corti is a special sensory ridge found on top of the basilar membrane in the cochlea of the inner ear. It contains many hair cells arranged in four rows, which are crucial for hearing. These hair cells have tiny hair-like structures called stereocilia that stick out from their top parts. A stiff, gel-like tectorial membrane lies over the organ of Corti. When sound waves cause vibrations, the stereocilia touch the tectorial membrane. This contact helps change the sound vibrations into electrical signals that the brain can understand as sound.
In simple words: The organ of Corti is inside your ear, on a special membrane. It has tiny hair cells that touch another membrane when sound comes. This touch changes sound vibrations into electrical messages for your brain, so you can hear.

🎯 Exam Tip: Focus on explaining how the mechanical movement of stereocilia against the tectorial membrane converts sound vibrations into neural impulses, as this is the core function.

 

Question 25. Give an account of mechanism of sound?
Answer: The process of hearing begins when sound waves enter the external ear canal and make the eardrum vibrate. These vibrations are then passed on to the oval window through the three small bones (ossicles) in the middle ear. Since the eardrum is much larger than the oval window, the pressure on the oval window becomes about 17-20 times greater. This increased pressure causes the round window to bulge outwards and inwards, which makes the basilar membrane and the organ of Corti move up and down. These movements open and close tiny ion channels, creating an action potential (an electrical signal). This signal then travels along the cochlear nerve to the brain, where it is understood as sound.
In simple words: Sound waves make your eardrum shake, which moves tiny bones. These bones push on a window to your inner ear, making a special membrane move. This movement creates electrical signals that go to your brain, allowing you to hear.

🎯 Exam Tip: Remember the amplification effect of the ossicles and the role of the basilar membrane's movement in converting mechanical energy to electrical signals for accurate explanation.

 

Question 26. Differentiate the rods from cones.
Answer:

In simple words: Rods help you see in the dark, but only in black and white. Cones help you see colors when there is enough light.

🎯 Exam Tip: Focus on the key difference: rods for dim light and black/white vision, cones for bright light and color vision. Mentioning their respective pigments (rhodopsin and photopsin) also scores well.

 

Question 27. A man is chating with his family in this time a house fly sits on his back at once he lifts the hand and strikes the fly. How can he know that? What are the structures involved in this perception?
(A diagram showing various skin receptors like Merkel disks, Root hair plexus, Pacinian corpuscle, Meissner corpuscle, Ruffini endings, etc., is present here in the source content.)
Answer: The man knows a fly is on his back because his skin, the largest sense organ, has many sensory receptors for pressure, heat, cold, and pain. These receptors send signals to his brain. When the fly landed, the skin's touch receptors were activated, sending a rapid signal to his brain which then processed the information and initiated the reflex action of lifting his hand. The key receptors involved in such a light touch perception include:
- **Tactile Merkel disc:** These are light touch receptors located deeper in the epidermis. They help detect sustained pressure and texture.
- **Hair follicle receptors:** These are also light touch receptors that are wrapped around hair follicles. They detect movements of hair, such as when a fly lands.
- **Meissner’s corpuscles:** These are small receptors found just beneath the epidermis in the dermal papillae. They are especially numerous in hairless skin areas like fingertips and soles of the feet and are sensitive to light pressure and touch.
- **Pacinian corpuscles:** These are large, egg-shaped receptors found deeper in the dermis. They detect different textures, temperature changes, hardness, and pain.
- **Ruffini endings:** These receptors, also in the dermis, respond to continuous pressure and skin stretch.
In simple words: The skin has special sensors that feel touch. When the fly landed, these sensors quickly sent a message to the brain. The brain then told the hand to move, causing the man to strike the fly.

🎯 Exam Tip: Explain the role of skin as a sensory organ and then list specific touch receptors and their functions. The quick, involuntary movement suggests a reflex arc involving these sensory inputs.

 

Question 28. Give notes on Defects of ear.
Answer: Defects of the ear can lead to hearing loss, which can be temporary or permanent. There are two main types of hearing loss:
**1. Conductive Deafness:** This happens when sound waves cannot reach the inner ear properly. Common causes include:
- **Blockage of the ear canal:** Often due to earwax buildup.
- **Rupture of the eardrum:** A hole in the eardrum can prevent proper vibration.
- **Middle ear infection:** Fluid buildup in the middle ear can block sound transmission.
- **Restriction of ossicular movement:** When the small bones (ossicles) in the middle ear cannot move freely.
**2. Sensory-neural Deafness:** This type occurs due to problems with the inner ear (specifically the organ of Corti) or the auditory nerve, or even in the ascending auditory pathways leading to the auditory cortex in the brain. This kind of hearing loss is usually more severe and often permanent.
In simple words: Ear problems can make it hard to hear. Some problems block sound from getting in, like earwax or a broken eardrum. Other problems are with the inner ear or the nerve that sends sound to the brain.

🎯 Exam Tip: Classify ear defects into conductive and sensory-neural hearing loss. For each type, provide common causes and briefly explain the underlying issue in the ear's structure.

 

Question 29. a) What is meant by proprioception? b) Give an account of organs of equilibrium?
Answer:
a) **Proprioception:** This is the body's ability to sense its own position, orientation, and movement in space. It allows us to know where our body parts are without looking, like touching our nose with our eyes closed. This sense is a fundamental part of maintaining balance and coordinating movements.
b) **Organs of Equilibrium:** The vestibular system in the inner ear is the primary organ of balance. It's made up of fluid-filled sacs and tubules, which detect head movements and position.
- **Semicircular canals:** These three canals (posterior, lateral, and superior) are oriented at right angles to each other. Each canal has a swollen area at its end called an ampulla. Inside the ampulla, there is a sensory area called the crista ampullaris, which contains hair cells. These structures detect the rotational movements of the head, such as turning or spinning.
- **Utricle and Saccule:** These are two small sacs within the vestibule. They contain equilibrium receptor regions called maculae, which also have hair cells and calcareous particles called otoliths. The maculae detect linear movements of the head (like moving forward or tilting) and the pull of gravity. The otoliths increase the inertia, enhancing the detection of these movements.
In simple words: a) Proprioception is your body knowing where it is and how it is moving, even without looking. b) The ear has special parts called the vestibular system, including semicircular canals and two sacs (utricle and saccule), which help you keep your balance by sensing head movements and position.

🎯 Exam Tip: Define proprioception clearly. For equilibrium, describe the vestibular system, its components (semicircular canals, utricle, saccule), and the type of movement each detects (rotational vs. linear/gravity).

 

Question 30. Give notes on Gustatory receptors?
Answer: The sense of taste is often considered one of the most enjoyable senses. Our tongue is covered with many small bumps called papillae, which give it an abrasive feel and are home to most taste buds. Some taste buds are also scattered on the soft palate and the inner surface of the cheeks. Taste buds are tiny, flask-shaped structures that contain 50 to 100 specialized epithelial cells. These cells are mainly of two types: gustatory epithelial cells (taste cells) and basal epithelial cells (repairing cells). The gustatory cells have long microvilli, called gustatory hairs, that project through a taste pore to the surface. These gustatory hairs are the sensitive parts of the cells and have sensory dendrites that send taste signals to the brain. Basal cells act like stem cells, dividing and developing into new gustatory cells, as taste cells are dynamic and are replaced frequently.
In simple words: Gustatory receptors are taste buds, mainly on your tongue. They have special cells with tiny hairs that sense flavors. These cells send messages to your brain so you can taste food. New taste cells grow all the time because old ones get worn out.

🎯 Exam Tip: Explain that taste buds are found on papillae and contain gustatory cells. Highlight the role of gustatory hairs in detecting chemicals and sending signals to the brain.

 

Question 31. Describe the structure of the receptor involved with a diagram.
(A diagram showing the structure of a taste bud, including the tongue, taste bud, taste pore, gustatory hairs, gustatory epithelial cells, basal epithelial cells, nerve, and connective tissue, is present here in the source content.)
Answer: The taste receptor, also known as a taste bud, is a small, flask-shaped sensory organ, usually found on the papillae of the tongue. Each taste bud is a cluster of 50 to 100 epithelial cells and is responsible for detecting different tastes.
The two main types of cells within a taste bud are:
- **Gustatory epithelial cells (taste cells):** These are the actual sensory cells. They have long, hair-like extensions called gustatory hairs that project out through a tiny opening on the tongue's surface called the taste pore. These gustatory hairs are the sensitive parts that bind to taste molecules (chemicals from food). Sensory dendrites from nerves are connected to these cells and send electrical signals to the brain when stimulated.
- **Basal epithelial cells (repairing cells):** These cells act as stem cells. They divide and mature to replace the gustatory epithelial cells, which are constantly exposed to friction and chemicals from food and are replaced every 7-10 days. This continuous renewal ensures that our sense of taste remains sharp.
In simple words: Taste receptors are tiny taste buds, mostly on the tongue. They have special "taste cells" with little hairs that touch food chemicals and send taste signals to the brain. There are also "repair cells" that make new taste cells, so your taste always stays fresh.

🎯 Exam Tip: When describing taste receptors, mention their location on papillae and the two main cell types: gustatory cells with their sensory hairs for taste detection, and basal cells for regeneration.