Maharashtra Board Class 12 Biology Chapter 9 Control and Co ordination Solutions

Control And Co-Ordination Class 12 Exercise Question Answers Solutions Maharashtra Board

Class 12 Biology Chapter 9 Exercise Solutions Maharashtra Board

Biology Class 12 Chapter 9 Exercise Solutions

1. Multiple Choice Questions

Question 1. The nervous system of mammals uses both electrical and chemical means to send signals via neurons. Which part of the neuron receives impulse?
(a) Axon
(b) Dendron
(c) Nodes of Ranvier
(d) Neurilemma
Answer: (b) Dendron
In simple words: Dendrons are the branched projections of a neuron that receive signals from other neurons and transmit them towards the cell body. They are the primary receptive regions of a nerve cell.

🎯 Exam Tip: Understanding the basic structure of a neuron and the function of each part (dendron, axon, cell body) is crucial for explaining nerve impulse transmission.

Question 2.is a neurotransmitter.
(a) ADH
(b) Acetyl CoA
(c) Acetyl choline
(d) Inositol
Answer: (c) Acetyl choline
In simple words: Acetylcholine is a chemical messenger, or neurotransmitter, that plays a role in both the peripheral and central nervous systems, involved in muscle contraction and memory.

🎯 Exam Tip: Memorize key neurotransmitters and their primary functions for multiple-choice questions on nervous system chemistry.

Question 3. The supporting cells that produce myelin sheath in the PNS are
(a) Oligodendrocytes
(b) Satellite cells
(c) Astrocytes
(d) Schwann cells
Answer: (d) Schwann cells
In simple words: Schwann cells are a type of glial cell found in the Peripheral Nervous System (PNS) that form the myelin sheath around axons, insulating them and speeding up nerve impulse transmission.

🎯 Exam Tip: Differentiate between glial cells in the CNS (Oligodendrocytes, Astrocytes, Microglia, Ependymal cells) and PNS (Schwann cells, Satellite cells) and their specific functions.

Question 4. A collection of neuron cell bodies located outside the CNS is called
(a) tract
(b) nucleus
(c) nerve
(d) ganglion
Answer: (d) ganglion
In simple words: A ganglion is a cluster of nerve cell bodies and associated nerve fibers located outside the central nervous system, serving as relay points for nerve signals.

🎯 Exam Tip: Understand the terminology for nerve structures: ganglion (PNS cell bodies), nucleus (CNS cell bodies), nerve (PNS axons), and tract (CNS axons).

Question 5. Receptors for protein hormones are located
(a) in cytoplasm
(b) on cell surface
(c) in nucleus
(d) on Golgi complex
Answer: (b) on cell surface
In simple words: Protein hormones, being water-soluble, cannot pass through the lipid cell membrane, so their receptors are located on the outer surface of the target cell.

🎯 Exam Tip: Distinguish the mechanism of action for protein (peptide) hormones vs. steroid hormones, especially regarding the location of their receptors (cell surface vs. intracellular).

Question 6. If parathyroid gland of man Eire removed, the specific result will be
(a) onset of aging
(b) disturbance of Ca++
(c) onset of myxoedema
(d) elevation of blood pressure
Answer: (b) disturbance of Ca++
In simple words: The parathyroid glands regulate calcium levels in the blood, so their removal would lead to a significant disturbance in calcium ion (Ca++) homeostasis.

🎯 Exam Tip: Focus on the primary role of each endocrine gland and the consequences of its removal or dysfunction for high-scoring answers.

Question 7. Hormone thyroxine, adrenaline and non-adrenaline are formed from
(a) Glycine
(b) Arginine
(c) Ornithine
(d) Tyrosine
Answer: (d) Tyrosine
In simple words: Thyroxine (thyroid hormone) and adrenaline/nor-adrenaline (catecholamines) are all derived from the amino acid tyrosine.

🎯 Exam Tip: Learn the precursor molecules for important hormones as this is a common area for direct recall questions.

Question 8. Pheromones are chemical messengers produced by animals and released outside the body. The odour of these substance affects
(a) skin colour
(b) excretion
(c) digestion
(d) behaviour
Answer: (d) behaviour
In simple words: Pheromones are chemicals released by an organism into the environment that affect the behavior or physiology of other organisms of the same species.

🎯 Exam Tip: Understand the distinction between hormones (internal communication) and pheromones (external communication influencing behavior).

Question 9. Which one of the following is a set of discrete endocrine gland?
(a) Salivary glands, thyroid, adrenal, ovary
(b) Adrenal, testis, ovary, liver
(c) Pituitary, thyroid, adrenal, thymus
(d) Pituitary, pancreas, adrenal, thymus
Answer: (c) Pituitary, thyroid, adrenal, thymus
In simple words: Discrete endocrine glands are specialized organs that produce and secrete hormones directly into the bloodstream, distinguishing them from organs with both endocrine and exocrine functions.

🎯 Exam Tip: Be able to identify purely endocrine glands versus glands with mixed functions (e.g., pancreas, liver) in lists provided in MCQs.

Question 10. After ovulation, Graafian follicle changes into
(a) corpus luteum
(b) corpus albicans
(c) corpus spongiosum
(d) corpus callosum
Answer: (a) corpus luteum
In simple words: After the release of an egg during ovulation, the remnants of the Graafian follicle transform into the corpus luteum, which then produces hormones like progesterone.

🎯 Exam Tip: Know the stages of follicular development and the hormonal changes that occur during the ovarian cycle, including the formation and function of the corpus luteum.

Question 11. Which one of the following pairs correctly matches a hormone with a disease resulting from its deficiency?
(a) Parathyroid hormone - Diabetes insipidus
(b) Luteinising hormone - Diabetes mellitus
(c) Insulin - Hyperglycaemia
(d) Thyroxine - Tetany
Answer: (c) Insulin - Hyperglycaemia
In simple words: Deficiency of insulin leads to hyperglycemia, a condition characterized by high blood sugar levels, as insulin is crucial for glucose uptake by cells.

🎯 Exam Tip: Create a table mapping key hormones to their deficiency/excess diseases and the associated symptoms for quick revision.

Question 12.is in direct contact of brain in humans.
(a) Cranium
(b) Dura mater
(c) Arachnoid
(d) Pia mater
Answer: (d) Pia mater
In simple words: The pia mater is the innermost and most delicate of the three meninges, lying directly on the surface of the brain and spinal cord, closely following its contours.

🎯 Exam Tip: Understand the layers of the meninges (dura mater, arachnoid mater, pia mater) and their relative positions to the brain and skull.

2. Very Very Short Answer Questions.

Question 1. What is the function of red nucleus?
Answer: Red nucleus plays an important role in controlling posture and muscle tone, modifying some motor activities and motor coordination.
In simple words: The red nucleus helps regulate muscle movement, especially in controlling posture and refining motor coordination.

🎯 Exam Tip: When asked for functions of brain parts, provide specific roles rather than general statements to demonstrate detailed knowledge.

Question 2. What is the importance of corpora quadrigemina?
Answer: Corpora quadrigemina consists of 4 solid rounded structures, viz. superior and inferior colliculi. Superior colliculi control visual reflexes while inferior colliculi control auditory reflexes.
In simple words: Corpora quadrigemina processes visual and auditory information, specifically managing reflexes like tracking moving objects and responding to sudden sounds.

🎯 Exam Tip: Break down complex anatomical structures into their sub-components (e.g., superior vs. inferior colliculi) and their distinct functions for clarity.

Question 3. What does the cerebellum of brain control?
Answer: Cerebellum of brain is an important centre which maintains equilibrium of body, posture, balancing orientation, moderation of voluntary movements and maintenance of muscle tone.
In simple words: The cerebellum is vital for coordinating voluntary movements, maintaining balance, posture, and muscle tone, ensuring smooth and precise actions.

🎯 Exam Tip: Highlight the cerebellum's role in coordination and balance, as these are its most well-known and crucial functions.

Question 4. Name the three ear ossicles.
Answer: Malleus [hammer], incus [anvil] and stapes [stirrup].
In simple words: The three tiny bones in the middle ear, known as ossicles, are the malleus, incus, and stapes, which transmit sound vibrations to the inner ear.

🎯 Exam Tip: Remember the common names (hammer, anvil, stirrup) along with their scientific names for comprehensive recall.

Question 5. Name the anti abortion hormone.
Answer: Progesterone.
In simple words: Progesterone is often called the "anti-abortion hormone" because it maintains the uterine lining during pregnancy, preventing contractions that could lead to miscarriage.

🎯 Exam Tip: Relate hormones to their specific physiological roles, especially those critical for reproductive health and pregnancy.

Question 6. Name an organ which acts as temporary endocrine gland.
Answer: Placenta. Corpus luteum in ovary.
In simple words: The placenta and corpus luteum are temporary endocrine glands because they form during specific reproductive phases and secrete hormones essential for pregnancy.

🎯 Exam Tip: Identify temporary endocrine structures, like the placenta and corpus luteum, and understand why they are classified as such (i.e., not permanent glands).

Question 7. Name the type of hormones which bind to the DNA and alter the gene expression.
Answer: Steroid hormones.
In simple words: Steroid hormones can pass through the cell membrane and directly interact with DNA to change gene expression, influencing long-term cellular functions.

🎯 Exam Tip: Distinguish the mechanism of action of steroid hormones (intracellular, direct gene regulation) from protein hormones (cell surface receptors, second messengers).

Question 8. What is the cause of abnormal elongation of long bones of arms and legs and of lower jaw.
Answer: Hypersecretion of growth hormones in adults causes abnormal elongation of long bones of arms and legs and of lower jaw i.e. acromegaly.
In simple words: Excessive growth hormone secretion in adults leads to acromegaly, causing enlargement of bones and tissues, particularly in the face, hands, and feet.

🎯 Exam Tip: Be precise with terms like "hypersecretion" and "acromegaly" and remember that growth hormone effects differ between children (gigantism) and adults (acromegaly).

Question 9. Name the hormone secreted by the pineal gland.
Answer: Melatonin.
In simple words: The pineal gland secretes melatonin, a hormone crucial for regulating sleep-wake cycles and seasonal rhythms.

🎯 Exam Tip: Directly link glands to their primary hormones and their most significant functions, like the pineal gland to melatonin and circadian rhythms.

Question 10. Which endocrine gland plays important, role in improving immunity?
Answer: The endocrine gland, thymus plays an important role in improving immunity.
In simple words: The thymus gland is vital for the maturation of T-lymphocytes, which are crucial components of the adaptive immune system.

🎯 Exam Tip: Recognize the thymus as an important endocrine gland with a key role in the immune system, particularly T-cell development.

3. Match The Organism With The Type Of Nervous System Found In Them.

🎯 Exam Tip: For matching questions, eliminate obvious pairs first and then focus on the remaining options to ensure accuracy.

4. Very Short Answer Questions.

Question 1. Describe the endocrine role of islets of Langerhans.
OR
Islets of Langerhans.
Answer: Endocrine cells of pancreas form groups of cells called Islets of Langerhans. There are four kinds of cells in islets of Langerhans which secrete hormones.
1. Alpha (a) cells : They are 20% and secrete glucagon. Glucagon is a hyperglycemic hormone. It stimulates liver for glucogenolysis and increases the blood glucose level.
2. Beta (β) cells : They are 70% and secrete insulin. Insulin is a hypoglycemic hormone. It stimulates liver and muscles for glycogenesis. This lowers blood glucose level.
3. Delta (δ) cells : They are 5% and secrete somatostatin. Somatostatin inhibits the secretion of glucagon and insulin. It also decreases the gastric secretions, motility and absorption in digestive tract. In general it is a growth inhibiting factor.
4. PP cells or F cells : They form 5%. They secrete pancreatic polypeptide (PP) which inhibits the release of pancreatic juice.
In simple words: The Islets of Langerhans in the pancreas contain specialized cells (alpha, beta, delta, PP) that produce hormones like glucagon, insulin, somatostatin, and pancreatic polypeptide, which collectively regulate blood glucose levels and digestive functions.

🎯 Exam Tip: When describing cell types and their secretions, clearly state the percentage, the hormone secreted, and its primary effect (e.g., hyperglycemic/hypoglycemic).

Question 2. Mention the function of testosterone?
Answer: Testosterone is a steroid sex hormone secreted by testes and cortex of adrenal glands. It controls the secondary sexual characters in males.
In simple words: Testosterone, a steroid hormone, primarily drives the development and maintenance of male secondary sexual characteristics.

🎯 Exam Tip: When defining hormone functions, include its source (gland) and primary physiological effects.

Question 3. Give symptoms of the disease caused by hyposecretion of ADH.
Answer: Polydipsia, i.e. frequent thirst and polyuria, i.e. frequent urination are the symptoms of the disease caused by hyposecretion of ADH.
In simple words: Hyposecretion of ADH (Antidiuretic Hormone) causes Diabetes Insipidus, leading to excessive thirst (polydipsia) and frequent, dilute urination (polyuria) due to the kidneys' inability to reabsorb water properly.

🎯 Exam Tip: For hormone-related diseases, remember both the hormone imbalance (hypo/hypersecretion) and the distinctive symptoms.

5. Short Answer Questions

Question 1. Rakesh got hurt on his head when he fell down from his motorbike. Which inner membranes must have protected his brain? What other roles do they have to play
Answer:
1. When Rakesh fell down from his motorbike, the inner membranes that protected his brain were meninges, viz. dura mater, arachnoid membrane and pia mater. Morevover, CSF must have also acted as a shock absorber.
2. Dura mater : It is the outer tough membrane protective in function.
3. Arachnoid membrane : It is the middle web-like membrane which communicates with fluids of upper sub dural space and lower sub arachnoid space.
4. Pia mater : It is the innermost highly vascularised nutritive membrane in close contact with brain and spinal cord.
In simple words: The brain is protected by three layers of meninges- dura mater, arachnoid mater, and pia mater- along with cerebrospinal fluid (CSF), which act as physical barriers and shock absorbers. Each layer provides specific protection, nutrient supply, and waste removal.

🎯 Exam Tip: Describe the meningeal layers in order from outermost to innermost, and explain their individual contributions to brain protection and function.

Question 2. Injury to medulla oblongata may prove fatal.
OR
Injury to medulla oblongata causes sudden death. Explain.
Answer:
1. Medulla oblongata is the region of the brain that controls all the involuntary activities.
2. Vital activities such as heartbeats, respiration, vasomotor activities, peristalsis, etc. are under the control of medulla oblongata.
3. When medulla oblongata is injured, all these vital functions are instantly stopped.
4. Therefore, injury to medulla oblongata causes sudden death.
In simple words: The medulla oblongata controls essential involuntary functions like heart rate, breathing, and blood pressure; damage to this area immediately disrupts these vital processes, leading to sudden death.

🎯 Exam Tip: Emphasize the medulla oblongata's role in controlling vital reflex centers and how its damage directly impacts survival for a clear explanation.

Question 3. Distinguish between the sympathetic and parasympathetic nervous system on the basis of the effect they have on:
Heartbeat and Urinary Bladder.
Answer:

🎯 Exam Tip: When distinguishing between sympathetic and parasympathetic systems, always remember they have opposing effects on most organs and aim to provide a clear, concise comparison.

Question 4. While holding a tea cup Mr. Kothari's hands rattle. Which disorder he may be suffering from and what is the reason for this?
Answer:
1. This condition is due to Parkinson's disease.
2. It is due to degeneration of dopamine- producing neurons in the CNS.
3. 80% of the patients develop this condition along with stiffness, difficulty in walking, balance and coordination.
In simple words: Mr. Kothari's trembling hands suggest Parkinson's disease, caused by the loss of dopamine-producing neurons in the brain, leading to motor symptoms like tremors, stiffness, and impaired balance.

🎯 Exam Tip: Link specific symptoms like "rattling hands" to neurological disorders and clearly explain the underlying physiological cause (e.g., neurotransmitter deficiency).

Question 5. List the properties of the nerve fibres.
Answer:
1. Excitability / irritability
2. Conductivity
3. Stimulus
4. Summation
5. All or none
6. Refractory period
7. Synaptic delay
8. Synaptic fatigue
9. Velocity.
In simple words: Nerve fibers possess several key properties including excitability (response to stimuli), conductivity (transmitting impulses), and properties related to signal integration like summation and synaptic delay.

🎯 Exam Tip: List properties clearly and concisely, focusing on terms that describe how nerves initiate, transmit, and process signals.

Question 6. How does tongue detect the sensation of taste?
Answer:
1. The surface of tongue is with gustatoreceptors.
2. These receptors are sensitive to the chemicals [sweet, salt, sour, bitter and umami (savory)] present in the food.
3. The receptor cells get stimulated, generate the impulse which is given to the sensory neuron.
In simple words: The tongue detects taste through gustatoreceptors on its surface, which are specialized cells that respond to specific chemical compounds (sweet, salty, sour, bitter, umami) in food, converting these chemical signals into electrical impulses for the brain.

🎯 Exam Tip: Explain the process sequentially: receptor type, what it detects, and how the signal is transmitted to the brain, including the five basic tastes.

Question 7. State the site of production and function of Secretin, Gastrin and Cholecystokinin.
Answer:

🎯 Exam Tip: For hormones, always specify both their site of production and their primary function, especially when asked for details in a table format.

Question 8. An adult patient suffers from low heart rate, low metabolic rate and low body temperature. He also lacks alertness, intelligence and initiative. What can be this disease? What can be its cause and cure ?
Answer:
1. The above symptoms indicate that the person is suffering from Myxoedema.
2. Myxoedema is condition caused due to hypothyroidism.
3. Hypothyroidism causes deficiency of thyroid hormones like T3 and T4 (thyroxine). This results in low BMR.
4. This condition can be cured by giving injections of thyroxine or tablets containing hormone preparation.
In simple words: The symptoms of low heart rate, metabolic rate, body temperature, and reduced mental function suggest Myxoedema, a condition caused by hypothyroidism (deficiency of thyroid hormones T3 and T4) and treatable with thyroxine supplements.

🎯 Exam Tip: When presenting a case study, clearly state the suspected disease, its root cause (hormonal imbalance), and the recommended treatment, linking symptoms directly to the disease.

Question 9. Where is the pituitary gland located? Enlist the hormones secreted by anterior pituitary.
Answer: The pituitary gland is attached to hypothalamus on the ventral surface of brain. It is lodged in a bony depression called sella turcica of sphenoid bone.
For names of hormones:
1. GH : [Growth Hormone/STH : Somatotropic Hormone]
2. TSH/TTH - [Thyroid Stimulating Hormone/ Thyrotropic Hormone]
3. ACTH - [adrenocorticotropic hormone]
4. PRL - [prolactin]
Gonadotropins-
1. FSH [follicle stimulating hormone]
2. LH/ICSH - [leutinizing hormone/ interstitial cells stimulating hormone]
In simple words: The pituitary gland, located at the base of the brain in the sella turcica, secretes various hormones from its anterior lobe including Growth Hormone, Thyroid Stimulating Hormone, ACTH, Prolactin, FSH, and LH, which regulate diverse bodily functions.

🎯 Exam Tip: For questions about glands, provide both the anatomical location and a comprehensive list of the hormones it secretes, including their full names/abbreviations.

Question 10. Explain how the adrenal medulla and sympathetic nervous system function as a closely integrated system.
Answer:
1. Adrenal medulla originates from embryonic neuro - ectoderm.
2. It consists of rounded group of large granular cells called chromaffin cells. They are modified post-ganglionic cells of sympathetic nervous system which have lost normal processes and acquired glandular function.
3. These cells are connected with pre-ganglionic fibres of sympathetic nervous system.
4. Hence adrenal medulla is an extension of sympathetic nervous system.
5. Thus adrenal medulla and sympathetic nervous system functions as a closely integrated system.
In simple words: The adrenal medulla acts as a modified sympathetic ganglion, directly releasing adrenaline and nor-adrenaline into the bloodstream when stimulated by the sympathetic nervous system, thereby amplifying and prolonging the body's "fight-or-flight" response.

🎯 Exam Tip: Highlight the embryological origin and the "modified ganglion" nature of the adrenal medulla to explain its close functional relationship with the sympathetic nervous system.

Question 11. Name the secretion of alpha, beta and delta cells of islets of Langerhans. Explain their role.
Answer:

🎯 Exam Tip: Clearly link each cell type (alpha, beta, delta) to its specific hormone and the primary action of that hormone, especially concerning blood glucose regulation.

Question 12. Which are the two types of goitre? What are their causes?
Answer:
(1) Goitre is the enlargement of thyroid gland. It is easily visible at the base of neck when a person is suffering from it.
(2) Goitre is of two types.
1. Simple goitre : It is also called endemic goitre. This is due to iodine deficiency in the food. This causes iodine deficit in blood. In an attempt to take more iodine from blood, the blood supply to the gland increases. This results in swelling on the thyroid.
2. Exophthalmic goitre : It is also called toxic goitre. This is due to hyperactive thyroid gland. This can happen if there is overstimulation of thyroid due to excess of ACTH. This disorder is also called Grave's disease or hyperthyroidism.
In simple words: Goitre, or thyroid enlargement, has two main types: simple goitre, caused by iodine deficiency, and exophthalmic goitre (Grave's disease), caused by an overactive thyroid gland often due to autoimmune issues or excess ACTH stimulation.

🎯 Exam Tip: When discussing types of a disease, define each type, state its specific cause, and mention any alternative names for clarity and completeness.

Question 13. Name the ovarian hormone and give their functions.
Answer:

🎯 Exam Tip: For reproductive hormones, detail their specific roles in sexual development, pregnancy, and birth to show a thorough understanding.

6. Answer The Following.

Complete the table.
Answer:

🎯 Exam Tip: When completing tables, ensure each cell contains accurate and concise information, clearly differentiating between similar-sounding cell types by their location and specific function.

7. Long Answer Questions.

Question 1. Explain the process of conduction of nerve impulses up to development of action potential.
Answer:
1. The origin and maintenance of resting potential depends on the original state of no stimulation.
2. Any stimulus or disturbance to the membrane will make the membrane permeable to Na+ ions. This causes rapid influx of Na+ ions.
3. The voltage gated Na+/K+ channels are unique. They can change the potential difference of the membrane as per the stimulus received and also the gates operate separately and are self closing.
4. During resting potential, both gates are closed and resting potential is maintained.
5. However during depolarization, the Na⁺ channels open but not the K+ channels. This causes Na⁺ to rush into the axon and bring about a depolarisation. This condition is called action potential.
6. Extra cellular fluid (ECF) becomes electronegative with respect to the inner membrane which becomes electropositive.
In simple words: Nerve impulse conduction begins when a stimulus causes the neuron membrane to become permeable to Na⁺ ions, leading to a rapid influx of Na⁺ and depolarization. This change in electrical potential across the membrane, where the inside becomes electropositive relative to the outside, generates an action potential.

🎯 Exam Tip: When explaining action potential, clearly detail the role of specific ion channels (Na⁺, K⁺), the movement of ions, and the resulting changes in membrane potential during depolarization.

Question 2. Draw the neat labelled diagrams.
a. Human ear.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव कान की संरचना को दर्शाता है, जिसमें बाहरी कान (ऑरिकल, ईयरलोब), मध्य कान (कर्णपटल, ऑडिटरी ट्यूब, मैलियस, इनकस, स्टेप्स) और आंतरिक कान (अर्धवृत्ताकार नलिकाएं, वेस्टिबुलर तंत्रिका, कोक्लीयर तंत्रिका, कोक्लिया) के सभी प्रमुख भाग स्पष्ट रूप से नामांकित हैं। यह ध्वनि तरंगों के संचरण और संतुलन बनाए रखने के लिए जिम्मेदार जटिल संरचनाओं को समझाता है।

🎯 Exam Tip: When asked to draw and label a diagram, ensure all key anatomical parts are accurately depicted and clearly labeled, as precise labeling is crucial for scoring marks.

b. Sectional view of human eye.
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव आँख के अनुभागीय दृश्य को दर्शाता है, जिसमें कॉर्निया, आईरिस, प्यूपिल, लेंस, स्क्लेरा, रेटिना, कोरॉइड, विट्रियस चैंबर, फोविया, ब्लाइंड स्पॉट, जलीय चैंबर, सस्पेंसरी लिगामेंट और ऑप्टिक तंत्रिका जैसे सभी आवश्यक भाग स्पष्ट रूप से नामांकित हैं। यह आँख की आंतरिक संरचना और प्रकाश को संसाधित करने में उसके विभिन्न घटकों की भूमिका को समझने में मदद करता है।

🎯 Exam Tip: For diagrams like the human eye, focus on depicting the layered structure and the optical components, ensuring distinct labeling for each part's contribution to vision.

c. Draw the neat labelled diagram of sagittal section or L.S. of human brain
Answer:
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव मस्तिष्क के अनुदैर्ध्य खंड (L.S.) को दर्शाता है, जिसमें सेरिब्रम, कॉर्पस कैलोसम, थैलेमस, हाइपोथैलेमस, पिट्यूटरी ग्रंथि, मिड ब्रेन, पॉन्स वेरोली, मेडुला ऑबलोंगाटा, सेरिबैलम, स्पाइनल कॉर्ड और पाइनियल ग्रंथि जैसे सभी प्रमुख क्षेत्र स्पष्ट रूप से नामांकित हैं। यह मस्तिष्क के विभिन्न कार्यात्मक क्षेत्रों और उनके अंतर-संबंधों की स्थानिक व्यवस्था को समझने में सहायक है।

🎯 Exam Tip: In a sagittal section of the brain, prioritize clear differentiation and labeling of the major brain regions (forebrain, midbrain, hindbrain) and key structures like the cerebrum, cerebellum, and brainstem components.

Question 2. Draw the neat labelled diagrams.
a. Human ear.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव कान की संरचना को दर्शाता है, जिसमें बाहरी कान (ऑरिकल, ईयरलोब, ऑडिटरी कैनाल), मध्य कान (इयरड्रम, टिम्पेनिक कैविटी, मैलियस, इन्कस, स्टेप्स) और आंतरिक कान (सेमीसर्कुलर डक्ट्स, वेस्टिबुलर नर्व, कोक्लियर नर्व, कोक्लिया, ऑडिटरी ट्यूब) शामिल हैं। यह सुनने और संतुलन के लिए जिम्मेदार विभिन्न भागों को उजागर करता है।
Answer: [Diagram is replaced by the explanation above.]
In simple words: The human ear is an intricate organ responsible for hearing and balance, composed of outer, middle, and inner parts, each with specialized structures to process sound and maintain equilibrium.

🎯 Exam Tip: Labeling all parts accurately in the diagram is crucial for full marks, especially differentiating between ossicles and inner ear structures.

b. Sectional view of human eye.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव आँख का एक अनुभागीय दृश्य प्रस्तुत करता है, जिसमें बाहरी परत (स्क्लेरा), मध्य परत (कोरोइड, आईरिस, सिलिअरी बॉडी/सस्पेंसरी लिगामेंट), और आंतरिक परत (रेटिना, फोविया, ब्लाइंड स्पॉट) जैसे प्रमुख भाग दिखाई देते हैं। लेंस, प्यूपिल, एक्वस और विट्रियस चैंबर, और ऑप्टिक नर्व भी स्पष्ट रूप से दर्शाए गए हैं, जो प्रकाश को संसाधित करने और मस्तिष्क तक भेजने के लिए आंख के कार्य को समझाते हैं।
Answer: [Diagram is replaced by the explanation above.]
In simple words: The human eye's sectional view reveals its complex structure, with layers like the sclera, choroid, and retina, along with components like the lens, iris, and optic nerve, all working together for vision.

🎯 Exam Tip: For the eye diagram, ensure correct placement and labeling of the cornea, lens, retina, and optic nerve, as these are key functional areas.

c. Draw the neat labelled diagram of sagittal section or L.S. of human brain
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र मानव मस्तिष्क के अनुदैर्ध्य काट (L.S.) को दर्शाता है, जिसमें सेरिब्रम, सेरिबैलम, और ब्रेनस्टेम (मिडब्रेन, पॉन्स वैरोली, मेडुला ऑब्लोंगाटा) जैसे मुख्य भाग शामिल हैं। इसमें थैलेमस, हाइपोथैलेमस, पीयूष ग्रंथि, कॉर्पस कैलोसम, केंद्रीय और पैरिएटो-ओसिपिटल सल्कस, कोरोइड प्लेक्सस, पीनियल ग्रंथि, आर्बर विटे, और पार्श्व वेंट्रिकल जैसे आंतरिक संरचनाओं को भी दर्शाया गया है। यह मस्तिष्क के विभिन्न क्षेत्रों को दिखाता है जो विभिन्न शारीरिक कार्यों को नियंत्रित करते हैं।
Answer: [Diagram is replaced by the explanation above.]
In simple words: The sagittal section of the human brain illustrates its major divisions like the cerebrum, cerebellum, and brainstem, alongside key internal structures that control various body functions.

🎯 Exam Tip: When drawing the brain's sagittal section, highlight the cerebrum, cerebellum, thalamus, hypothalamus, and brainstem clearly, as these are fundamental regions.

d. Draw the neat labelled diagram of Multipolar Neuron.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक मल्टीपोलर न्यूरॉन की संरचना को दर्शाता है, जिसमें कोशिका शरीर (सोमा) नाभिक और न्यूक्लियोलस के साथ, डेंड्राइट्स, एक्सॉन हिलॉक, प्रारंभिक खंड, एक्सॉन माइलिन शीथ और श्वान कोशिकाओं के साथ, रैनवियर के नोड्स, न्यूरोफाइब्रिल्स, निस्सल बॉडीज़ और सिनाप्टिक नॉब्स शामिल हैं। यह न्यूरॉन के माध्यम से संकेत संचरण की दिशा भी दिखाता है, जो तंत्रिका आवेगों को प्राप्त करने, संसाधित करने और संचारित करने के लिए इसकी जटिल बनावट को दर्शाता है।
Answer: [Diagram is replaced by the explanation above.]
In simple words: A multipolar neuron diagram illustrates its main parts-dendrites, cell body, and axon-which are specialized for receiving, processing, and transmitting electrical signals within the nervous system.

🎯 Exam Tip: For the multipolar neuron, ensure the dendrites, cell body (soma) with nucleus, axon, myelin sheath, Nodes of Ranvier, and synaptic knobs are all distinctly labeled.

Question 3. Answer the questions after observing the diagram given below.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक सिनेप्स (तंत्रिका कोशिकाओं के बीच का जंक्शन) को दर्शाता है। इसमें प्रीसिनेप्टिक न्यूरॉन, सिनेप्टिक एंड बल्ब जिसमें न्यूरोट्रांसमीटर से भरी सिनेप्टिक वेसिकल्स होती हैं, वोल्टेज-गेटेड Ca++ चैनल, सिनेप्टिक क्लेफ्ट और पोस्टसिनेप्टिक न्यूरॉन पर न्यूरोट्रांसमीटर रिसेप्टर्स और लिगैंड-गेटेड आयन चैनल दिखाए गए हैं। यह तंत्रिका आवेगों के रासायनिक संचरण की प्रक्रिया को स्पष्ट करता है, जहां न्यूरोट्रांसमीटर सिनेप्टिक क्लेफ्ट को पार करते हैं और पोस्टसिनेप्टिक न्यूरॉन को सक्रिय करते हैं।
Answer: [Diagram is replaced by the explanation above.]
a. What do the synaptic vesicles contain?
Answer: Synaptic vesicles contain a neurotransmitter - acetyl choline.
b. What process is used to release the neurotransmitter ?
Answer: Exocytosis.
c. What should be the reason for the next impulse to be conducted?
Answer: Removal of neurotransmitter by the action of acetyl cholinesterase.
d. Will the impulse be carried by post synaptic membrane even if one pre-synaptic neuron is there?
Answer: As far as impulse is transmitted by pre-synaptic neuron, it will be received by post-synaptic neuron.
e. Can you name the channel responsible for their transmission?
Answer: Ca++ channel
In simple words: Synaptic vesicles store neurotransmitters, which are released via exocytosis to transmit signals across a synapse, where they bind to receptors and are then removed to allow for subsequent impulses.

🎯 Exam Tip: Understanding the roles of neurotransmitters, vesicles, and receptors at the synapse is crucial for comprehending nerve impulse transmission.

Question 4. Explain the Reflex Pathway with the help of a neat labelled diagram.
OR
With the help of a neat and labelled diagram, describe reflex arc.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र एक प्रतिवर्त क्रिया और प्रतिवर्त चाप को दर्शाता है, जिसमें ग्रे मैटर और व्हाइट मैटर के साथ रीढ़ की हड्डी का अनुभागीय दृश्य शामिल है। यह डोर्सल रूट गैंग्लियन, डोर्सल रूट, वेंट्रल रूट, रमुस डोर्सलिस, रमुस वेंट्रलिस, और सिम्पेथेटिक गैंग्लियन कम्युनिकन्स को भी उजागर करता है। चित्र प्रतिवर्त क्रिया के पांच मुख्य घटकों-रिसेप्टर अंग, संवेदी न्यूरॉन, एसोसिएशन न्यूरॉन, मोटर न्यूरॉन और इफेक्टर अंग-को स्पष्ट करता है, जो केंद्रीय तंत्रिका तंत्र के माध्यम से बिना सचेत प्रयास के प्रतिक्रिया का मार्ग दिखाता है।
Answer: [Diagram is replaced by the explanation above.]
I. Reflex action : Reflex action Is defined as a quick, automatic involuntary and often unconscious action brought about when the receptors are stimulated by external or internal stimuli.
II. Reflex arc : Reflex actions are controlled by CNS. Reflex arc is the structural or functional unit of reflex action. Simple reflex arc is formed of the following five components.
(1) Receptor organ : The sensory part that receives the stimulus is called receptor organ. It can be any sense organ that receives the stimulus and converts it into the impulse, e.g. skin, eye, ear, tongue, nasal epithelium, etc.
(2) Sensory neuron or afferent neuron:
Sensory part carrying impulse from receptor organ to CNS is called sensory neuron. Its cyton is located in dorsal root ganglion. Its dendron is long and connected to receptor while the axon enters in the grey matter of spinal cord to form a synapse.
(3) Association, adjustor or intermediate neuron : It is present in the grey matter of spinal cord. Receiving impulse from sensory neuron, interpreting it and generating motor impulse are done by association neuron.
(4) Motor neuron (effector) : The cyton of motor neuron is present in the ventral horn of grey matter and axon travels through ventral root. It conducts motor impulse from spinal cord to effector organ.
(5) Effector organ : Effector organ is a specialized part of the body which is excited by receiving the motor impulse. It gives proper response to the stimulus, e.g. muscles or glands. The path of reflex action is followed by the unidirectional impulse. It originates in the receptor organ and ends in effector organ through CNS.
In simple words: A reflex action is a rapid, automatic, and involuntary response to a stimulus, carried out through a reflex arc, which involves a receptor, sensory neuron, interneuron, motor neuron, and effector organ, bypassing conscious brain processing for speed.

🎯 Exam Tip: Clearly defining each component of the reflex arc and illustrating the unidirectional path of the impulse is key for a complete answer.

Question 5. Krishna was going to school and on the way he saw a major bus accident. His heartbeat increased and hands and feet become cold. Name the part of the nervous system that had a role to play in this reaction.
Answer:
1. The symptoms observed in Krishna were due to sympathetic nervous system. Emergency conditions trigger sympathetic nervous system to stimulate adrenal medulla.
2. The cells of adrenal medulla secrete catecholamines like adrenaline and nor-adrenaline.
3. These hormones have direct effect on the pacemaker of the heart which causes increase in the heart rate and other associated symptoms.
4. This is a typical fright reaction caused by intervention of sympathetic nervous system.
In simple words: Krishna's physical reactions were due to the sympathetic nervous system, which, in response to the emergency, stimulated the adrenal medulla to release adrenaline, causing an increased heart rate and other 'fight-or-flight' responses.

🎯 Exam Tip: Remember to link specific physiological responses (like increased heart rate, cold hands/feet) to the actions of the sympathetic nervous system and its associated hormones (adrenaline/nor-adrenaline).

Question 6. What will be the effect of thyroid gland atrophy on the human body?
Answer:
1. Atrophy means degeneration. Atrophy of thyroid gland will result in deficient secretion of thyroid hormones leading to hypothyroidism. Deficiency of thyroid hormones [T3 and T4] and thyrocalcitonin will cause following effects on the body.
2. Decrease in BMR i.e. basal metabolic rate, decrease in the blood pressure, heart beat, body temperature, etc.
3. Occurrence of myxoedema in which there is abnormal deposition of fats under the skin giving puffy appearance in adults.
4. Irregularities in menstrual cycle in case of female patients.
5. Hair become brittle and fall.
6. Calcium metabolism also disturbs due to lack of thyrocalcitonin.
In simple words: Thyroid gland atrophy leads to hypothyroidism, causing a decrease in basal metabolic rate, myxoedema, menstrual irregularities, brittle hair, and disturbed calcium metabolism due to insufficient thyroid hormone production.

🎯 Exam Tip: Focus on the direct consequences of low thyroid hormone levels, such as reduced BMR, and specific conditions like myxoedema, ensuring you mention both T3/T4 and thyrocalcitonin effects.

Question 7. Write the names of hormones and the glands secreting them for the regulation of following functions
(a) Growth of thyroid and secretion of thyroxine.
Answer: TSH by adenohypophysis.
(b) Helps in relaxing pubic ligaments to facilitate easy birth of young ones.
Answer: Relaxin by degenerating corpus luteum of the ovary.
(c) Stimulate intestinal glands to secrete intestinal juice.
Answer: Secretin by duodenal mucosa.
(d) Controls calcium level in the blood.
Answer: Calcitonin [hypocalcemic hormone] by thyroid and parathormone [ hypercalcemic hormone] by parathyroid glands.
(e) Controls tubular absorption of water in kidneys.
Answer: ADH by hypothalamus.
(f) Urinary elimination of water.
Answer: Atrial natriuretic factor by atria of heart.
(g) Sodium and potassium ion metabolism.
Answer: Aldosterone by adrenal cortex.
(h) Basal Metabolic rate.
Answer: T3 and T4 by thyroid gland.
(I) Uterine contraction.
Answer: Oxytocin by hypothalamus.
(j) Heartbeat and blood pressure.
Answer: Adrenaline, non-adrenaline [stimulation] and acetylcholine [inhibition] by adrenal medulla.
(k) Secretion of growth hormone.
Answer: GHRF by hypothalamus.
(l) Maturation of Graafian follicle.
Answer: FSH by anterior pituitary.
In simple words: Hormones are chemical messengers secreted by specific glands that regulate a wide array of bodily functions, from growth and metabolism to reproduction and stress responses.

🎯 Exam Tip: Memorize the primary hormones for each physiological function and their secreting glands, as this is a common direct recall question type.

Question 8. Explain the role of hypothalamus and pituitary as a coordinated unit in maintaining homeostasis.
Answer:
1. Homeostasis is maintenance of constant internal environment of the body.
2. When certain hormones from any endocrine glands are secreted in excess quantity, the : inhibiting factors from hypothalamus, automatically exert negative feedback and stop the production of stimulating hormones from pituitary.
3. Similarly, if any hormone is in deficit, then j the concerned gland is given message through releasing factor. This way the hormone production remains in a balanced state or homeostasis.
4. E.g. If thyroxine from thyroid gland is secreted in excess, the secretion of TSH from pituitary is stopped by stopping the production of TRF from hypothalamus.
5. Though most of the endocrine glands are under the influence of pituitary gland, it is in turn controlled by hypothalamus.
6. Hypothalamus secretes releasing factors and inhibiting factors and hence regulate the secretions of pituitary (hypophysis).
7. There is negative feedback mechanism in controlling the secretions of the endocrine glands.
8. Hypothalamus forms the hypothalamo-hypophyseal axis through which transportation of neurohormones take place.
Following are the releasing and inhibiting factors produced by hypothalamus:
1. Somatotropin/GHRF : It stimulates release of growth hormone.
2. Somatostatin/GHRIF : It inhibits the release of growth hormone.
3. Adrenocorticotropin Releasing Hormone / CRF : It stimulates the release of ACTH by the anterior pituitary gland.
4. Thyrotropin Releasing Hormone /TRF : It stimulates the release of TSH by anterior pituitary gland.
5. Gonadotropin Releasing Hormone (GnRH) : It stimulates pituitary to secrete gonadotropins.
6. Prolactin Inhibiting Hormone (Prolactostatin) : It inhibits prolactin released by anterior pituitary gland.
7. Gastrin Releasing Peptide (GRP).
8. Gastric Inhibitory Polypeptide (GIP).
In simple words: The hypothalamus and pituitary gland work together as a master control unit for the endocrine system, with the hypothalamus secreting releasing and inhibiting factors that regulate pituitary hormone secretion, which in turn controls other endocrine glands, all operating via negative feedback to maintain the body's internal balance or homeostasis.

🎯 Exam Tip: Emphasize the negative feedback loops and the hypothalamo-hypophyseal axis as central to the coordinated function of these two glands in maintaining homeostasis.

Question 9. What is adenohypophysis ? Name the hormones secreted by it.
Answer:
1. Adenohypophysis is the large anterior lobe of pituitary gland.
2. It is derived from embryonic ectoderm in the form of Rathke's pouch which is a small outgrowth from the roof of embryonic stomodaeum.
3. It is made up of epitheloid secretory cells.
It secretes following hormones:
1. GH : [Growth Hormone/STH : Somatotropic Hormone]
2. TSH/TTH - [Thyroid Stimulating Hormone/ Thyrotropic Hormone]
3. ACTH - [adrenocorticotropic hormone]
4. PRL - [prolactin]
Gonadotropins-
1. FSH [follicle stimulating hormone]
2. LH/ICSH - [leutinizing hormone/ interstitial cells stimulating hormone]
In simple words: The adenohypophysis is the anterior part of the pituitary gland, originating from embryonic ectoderm, and it secretes several vital hormones like Growth Hormone, TSH, ACTH, Prolactin, FSH, and LH, which regulate various bodily functions.

🎯 Exam Tip: Clearly list all major hormones secreted by the adenohypophysis along with their full names or common abbreviations, as this is often tested for comprehensive knowledge.

Question 10. Describe, in brief, an account of disorders of adrenal gland.
Answer:
(1) Disorders of adrenal cortical secretions are caused due to hyposecretion and hypersecretion of adrenal corcoid hormones.
(2) Hyposecretion of corticosteroids causes Addison's disease.
(3) The symptoms of Addison's disease are low blood sugar, low body temperature, feeble heart action, low BR acidosis, low Na+ and K+ concentration in plasma, excessive loss of Na⁺ and water in urine, impaired kidney functioning and kidney failure, etc. it leads to weight loss, general weakness, nausea, vomiting and diarrhoea.
(4) Hypersecretion of corticoids causes Cushing's disease.
(5) The symptoms of Cushing's disease are high blood sugar level, glucosuria, alkalosis, enhancement of total quantity of electrolytes in extracellular fluid, polydipsia, increased BR muscle paralysis, obesity, wasting of limb muscles, etc.
In simple words: Adrenal gland disorders arise from either too little (hyposecretion) or too much (hypersecretion) corticosteroid production, leading to conditions like Addison's disease (low blood sugar, weakness) or Cushing's disease (high blood sugar, obesity, muscle wasting), respectively.

🎯 Exam Tip: Distinguish clearly between Addison's disease (hyposecretion) and Cushing's disease (hypersecretion), listing at least three characteristic symptoms for each to show comprehensive understanding.

Question 11. Explain action of steroid hormones and proteinous hormones.
OR
Explain the mode of action of steroid hormones.
Answer:
The hormones always act on their target organs or tissues to induce their effects. The target tissues have specific binding sites or receptor sites which contain hormone receptors.
I. Steroid hormones:
1. The steroid hormones are lipid soluble and can easily cross the lipoproteinous plasma membrane.
2. The hormone receptors for steroid hormones are present in cytoplasm or in nucleus.
3. Hormone-receptor complex formed in cytoplasm enters the nucleus and regulate the gene expression or chromosome function.
4. In some cases the receptors are present inside the nucleus where hormone-receptor complex is formed.
5. These complexes interact with the genome to evoke biochemical changes that result in physiological and developmental functions.
II. Protein hormones:
1. The hormone receptors for protein hormones are present on the cell membrane (i.e. membrane bound receptors).
2. When the hormone binds to its receptor, it forms hormone-receptor complex. Each receptor is specific to a specific hormone.
3. The hormones which interact with membrane bound receptors normally do not enter the target cell but generate second messengers. Such as cyclic AMP Ca++ or IP (Inositol triphosphate), etc.
4. This leads to certain biochemical changes : in the target tissue.
5. Thus, the tissue metabolism and consequently the physiological functions are regulated by hormones.
In simple words: Steroid hormones, being lipid-soluble, enter target cells to bind with intracellular receptors, directly influencing gene expression, while protein hormones bind to cell surface receptors, triggering secondary messengers inside the cell to initiate physiological changes without entering.

🎯 Exam Tip: Differentiate clearly between the intracellular action of steroid hormones and the membrane-bound receptor and second messenger system of protein hormones; this distinction is a core concept.

Question 12. Describe in brief an account of disorders of the thyroid.
OR
What are the functional disorders of thyroid gland? Describe in brief.
Answer:
Disorders of thyroid gland are of three types, viz. hypothyroidism, hyperthyroidism and simple goitre.
(1) Hypothyroidism : Hyposecretion of thyroxine. This hyposecretion causes two types of disorders, viz. cretinism in children and myoxedema in adults.
(i) Cretinism : Hyposecretion of thyroxine in childhood causes cretinism. The symptoms of cretinism are retardation of physical and mental growth.
(ii) Myxoedema : Deficiency of thyroxine in adults causes this disorder. It is also referred to as Gull's disease. Symptoms are thickening and puffiness of the skin and subcutaneous tissue particularly of face and extremities. Patients with low BMR. It also causes mental dullness, loss of memory, slow action.
(2) Hyperthyroidism : Excessive secretion of thyroxine causes exophthalmic goitre or Grave's disease. There is slight enlargement of thyroid gland. It increases BMR, heart rate, pulse rate and BE Reduction in body weight due to rapid oxidation, nervousness, irritability. Peculiar symptom is exophthalmos, i.e. bulging of eyeballs with staring look and less blinking. This is caused by deposition of fats behind the eye balls in eye sockets. There is muscular weakness and loss of weight.
(3) Simple goitre (Iodine deficiency goitre) : Simple goitre occurs due to deficiency of iodine in diet or drinking water. Simple goitre causes enlargement of thyroid gland. Thyroid gland in an attempt to get more iodine from the blood, swells due to increased blood supply. Prevention of goitre can be done by administering iodized table salt. It is also called endemic goitre as it is common in hilly areas.
In simple words: Thyroid disorders include hypothyroidism (low thyroid hormone, causing cretinism in children and myxoedema in adults), hyperthyroidism (excessive thyroid hormone, leading to exophthalmic goitre or Grave's disease), and simple goitre (thyroid enlargement due to iodine deficiency).

🎯 Exam Tip: When describing thyroid disorders, clearly define hypothyroidism and hyperthyroidism, list their respective diseases (cretinism, myxoedema, Grave's disease), and explain their causes (deficiency/excess of thyroxine, iodine deficiency) with key symptoms.