Selina Concise Solutions for ICSE Class 8 Biology Chapter 7 Nervous System

REVIEW QUESTIONS

Multiple Choice Questions:

1. Put a tick mark (✓) against the correct alternative in the following statements:

(a) Medulla oblongata controls
1. Smelling
2. Beating of heart and respiratory movement
3. Intelligence and will power
4. Balancing the body

Answer: 2. Beating of heart and respiratory movement
The medulla oblongata acts as the control center for essential life functions that happen automatically. It ensures your heart keeps pumping and your lungs keep breathing without you having to think about it.
Teacher's Tip: Think of the Medulla as the "Machine" that keeps the body's vital systems running.
Exam Tip: Always associate the medulla with involuntary actions like heartbeat and breathing.

(b) Balance of body is controlled by:
1. Spinal cord
2. Cerebellum
3. Cerebrum
4. Medulla

Answer: 2. Cerebellum
The cerebellum coordinates muscular activity to maintain posture and equilibrium. It allows you to walk in a straight line or ride a bicycle by managing your physical balance.
Teacher's Tip: Remember "Bell" in Cerebellum - it rings to keep you balanced!
Exam Tip: If the question mentions "muscular coordination" or "equilibrium," the answer is always the cerebellum.

(c) The smell of good food causes watering of your mouth. It is a
1. Natural reflex
2. Acquired relfex
3. Inborn reflex
4. Ordinary reflex

Answer: 2. Acquired relfex
An acquired reflex is one that develops through experience or learning during your lifetime. Since you have learned to associate the smell of food with its delicious taste, your mouth begins to water in anticipation.
Teacher's Tip: Acquired reflexes are "learned" like typing or playing an instrument.
Exam Tip: Contrast this with natural reflexes like blinking, which you are born knowing how to do.

(d) The structural and functional unit of nervous system is a
1. Axon
2. Nephron
3. Neuron
4. Texon

Answer: 3. Neuron
Neurons are the specialized cells that carry electrical messages throughout the entire nervous system. They are the basic building blocks that allow the brain to communicate with the rest of the body.
Teacher's Tip: Don't confuse "Neuron" with "Nephron," which belongs to the kidney (excretory system).
Exam Tip: Always use the term "nerve cell" and "neuron" interchangeably in descriptions.

Short Answer Questions:

Question 1: Name the two types of coordination which take place in our body.
Answer: (a) Nervous coordination: By nerves and brain
(b) Chemical coordination: By hormones
Coordination ensures that all parts of the body work together as a single, organized unit. It allows the body to react quickly to changes in the environment or manage long-term growth.
Teacher's Tip: Nervous coordination is like a fast "Electrical Wire," while Chemical coordination is like "Special Mail."
Exam Tip: For full marks, mention the specific medium for each (nerves/brain and hormones).

Question 2: Your are driving your bicycle at a fast speed. Suddenly, a small boy comes in front of your cycle and, without wasting any time in thinking, you immediately apply the brakes and accident is avoided. What name is given to such an action?
Answer: Reflex action (acquired).
This is an automatic and rapid response to a sudden stimulus to prevent harm. In this case, your brain has learned the action of braking so well that it happens without conscious thought.
Teacher's Tip: Reflex actions bypass the thinking part of the brain to save time in emergencies.
Exam Tip: Use the term "Acquired" if the reflex was learned through practice, like riding a bike.

Question 3: Given below is the diagram of a neuron. Name the parts numbered 1-5.
Answer: 1. Dendrite
2. Nucleus
3. Cell Body (Nyton)
4. Axon (Nerve fibre)
5. Node of Ranvier
These structures allow a single nerve cell to receive signals at one end and transmit them down a long path. The axon acts as the main transmission line for these electrical impulses.
Teacher's Tip: Think of the cell body as the "Headquarter" and the axon as the "Long Highway."
Exam Tip: Label diagrams with straight lines and ensure you distinguish between the dendrite and the axon.

Question 4: Write one word in the space provided to complete the second pair of the related words pertaining to nervous system.
Memory : cerebrum : : breathing :
Balance : cerebellum : : reasoning :
Answer: Memory : cerebrum : : breathing: medulla oblongata
Balance : cerebellum : : reasoning : cerebrum
This exercise shows how different parts of the brain are specialized for specific biological or mental tasks. The cerebrum is the "thinking" part, while the medulla handles the "living" parts like breathing.
Teacher's Tip: Link "Reasoning" and "Intelligence" directly to the Cerebrum.
Exam Tip: When doing analogy questions, look for the functional relationship (part-to-function).

Question 5: Differentiate between the following pair of terms:
(a) Stimulus and impulse
(b) Receptor and effector
(c) Motor nerve and sensory nerve
Answer: (a) Stimulus: Any change in the environment that usually results in change in the activity of the body.
Impulse: A wave of electrical disturbance that runs through the nerves.
(b) Receptor: The nerve cell on receiving the stimulus sets up the waves of impulses towards the central nervous system.
Effector: Any muscle or gland on receiving the impulse from the brain (or the spinal cord), contracts or secretes.
(c) Motor nerve: It contains only motor neurons,
Example: Nerves going to the muscles of the eyeball.
Sensory nerve: It contains only sensoiy neurons.
Example: optic nerve of the eye.
These pairs represent the "input" and "output" paths of the nervous system. Every action starts with a stimulus sensed by a receptor and ends with an impulse reaching an effector.
Teacher's Tip: Sensory = "Inbound traffic" to brain; Motor = "Outbound traffic" to muscles.
Exam Tip: Always provide an example when asked to differentiate between nerve types for extra clarity.

Question 6: (a) Name the three major divisions of the human nervous system.
(b) Name the three main parts of human brain.
Answer: (a)
1. The central nervous system (brain and spinal cord)
2. The peripheral nervous system
3. The autonomic nervous system
(b)
1. Cerebrum
2. Cerebellum
3. Medulla oblongata
The nervous system is organized into departments to handle different types of body control. The central part acts as the processor, while the peripheral part acts as the connecting wires.
Teacher's Tip: Brain + Spinal Cord = CNS (the command center).
Exam Tip: Do not mix up the "Nervous System divisions" with the "Brain parts" in your answer.

Question 7: Give the function of each of the following:
(a) Olfactory nerve:
(b) Optic nerve:
(c) Facial nerve:
Answer: (a) Olfactory nerve: The sense of smell is present in the epithelial layers of the nasal chambers. The sense of smell is carried to the brain by the olfactory nerve. They arise from the anterior ends of the olfactory lobes and are distributed to lining of nasal chambers.
(b) Optic nerve: It carries the reflection of the object from the retina to the brain. The image formed on the retina is in a reverted position and the correct picture is formed in the brain as the object is. The optic nerves arise from the side of diencephalon. They innervate the retina of the eye and are sensory in nature.
(c) Facial nerve: It carries message and all expressions of the face, mastication work alone by the teeth, movement of the neck and the activities of the salivary glands to the brain. It arises from the side of medulla. On the whole facial nerves are mixed in nature.
Cranial nerves are vital because they directly connect our sense organs and facial muscles to the brain. They allow us to see the world, smell food, and express our emotions through facial movements.
Teacher's Tip: Olfactory = Odor (Smell); Optic = Optical (Vision).
Exam Tip: Mention the nature of the nerve (Sensory or Mixed) when describing its function.

Long answer questions

Question 1: With the help of a suitable diagram describe the structures of a neuron.
Answer: Nervous system consists of special cells called nerve cells or neurons. It has a main cell body called cyton. It gives out many processes called dendrites. From it a very long process is given out. It is called axon or nerve fibre.
The cell body has a nucleus. The dendrites get the message from the organs and send this message to the axon through the cell body. Then the axon sends the message to muscles to contrast or to the gland for secretion.
The neurons make contact with one another through their processes. The axon at its end branches and meets the dendrites of another neuron. The meeting point is called synapse. The message is passed on from one axon to the dendrites of another neuron.
How the message goes ? It is like this:
Organ -> Message goes to dnedrites -> Cell body -> Axon -> Muscles or glands
The neuron is the primary communication cell, designed to send electrical pulses over long distances. The synapse acts as a tiny gate between neurons where the message is handed off chemically.
Teacher's Tip: Think of the Synapse as a "Gap" that the message must jump across to reach the next cell.
Exam Tip: Draw the flow chart showing the path of the message to summarize your long answer.

Question 2: Briefly describe the structure of the cerebrum in human brain and mention its functions.
Answer: Brain consists of main three parts and lies in the cranial cavity of skull.
1. The cerebrum
2. The cerebellum
3. The medulla oblongata
Cerebrum: It is very large and form two third of the whole brain. The two hemispheres are separated from each other by a deep longitudinal groove, the median fissure. The outer surface is folded with ridges and grooves. The hemispheres are hollow from inside and their walls have outer and inner portions. The outer portion has cell bodies of the neurons and it is called grey matter. The wavery edges of the folded layer has large number of neurons to the extent of 9 billion. The inner portion of the cerebrum has axons and it is called white matter.
Functions:
1. It controls all the voluntary activities.
2. It is the seat of intelligence, consciousness and will power.
The cerebrum's folded surface increases the area for neurons, allowing for complex thought and memory. It is essentially the "computer processor" for everything we consciously choose to do.
Teacher's Tip: More folds = more brain power (neurons).
Exam Tip: Be sure to distinguish between "Grey matter" (outer cell bodies) and "White matter" (inner axons).

Question 3: Mention the three functions of spinal cord.
Answer: Spinal cord has the following functions.
1. It is the centre of reflex actions below the neck.
2. It carries messages from the skin and muscles to the brain.
3. All the stimuli and responses are passed from and to the brain through the spinal cord.
The spinal cord acts as the main data cable connecting the brain to the rest of the body. It also handles quick reactions, like pulling your hand away from heat, without needing the brain's input.
Teacher's Tip: Think of the Spinal Cord as the "Information Superhighway" of the body.
Exam Tip: Emphasize its role in reflex actions as it is its most distinct function.

Question 4: With the help of suitable example, describe reflex action.
Answer: Reflex action: Reflex actions are automatic responses to stimuli. These actions are not under the control of the animal. They are of definite and mechanical type. Peripheral nervous system and spinal cord both control certain action and the brain is not in action. Some examples of reflex actions are:
1. Pupil becomes narrow when strong light falls on it.
2. The aroma of the food makes the mouth watering.
3. The hand is withdrawn as we touch the hot plate.
4. Flow of bile from the gall bladder into the duodenum.
5. A loud thud may lead to opening of the mouth.
In a reflex action brain is not involved, removing the hand on touching a hot plate is a reflex action. The impulse of heat goes from the hand to the spinal cord and the order is sent back to the muscles of the hand to remove the hand from the hot plate.
This rapid pathway, known as a reflex arc, allows the body to protect itself from danger before we even realize we are hurt. It saves precious seconds that could mean the difference between a small burn and a serious injury.
Teacher's Tip: Reflex = Automatic and Fast (bypass the brain).
Exam Tip: When describing a reflex action, always state that the "brain is not involved" initially.

Question 5: Describe three kinds of nerves, giving the example of each.
Answer: A nerve is formed by a group of nerve fibres (axons) encased by tubular medullary sheath. The medullary sheath acts as insulation and do not allow mixing up of impulses of the neighbouring axons (nerve fibres) We have three kinds of nerves:
1. Sensory nerve: It brings impulses from sense organs as these have sensory fibres. These nerve carry the impulses from the sense organs to the brain or to the spinal cord as optic nerve of the eye.
2. Motor nerves: These carry impulses to muscles or glands from the brain or spinal cord. These nerves have only motor fibres as nerves to the muscles of the eye ball.
3. Mixed nerve: It has both sensory and motors fibres as nerve going to the tongue.
Nerves are essentially bundles of specialized biological "wires" that transmit data. Insulation from the medullary sheath ensures that electrical signals don't jump between different paths incorrectly.
Teacher's Tip: Mixed nerves are like "Two-way streets" for electrical impulses.
Exam Tip: Provide the specific example for each nerve type (Eye, Tongue) to score full marks.

Question 6: Differentiate between natural reflex and conditioned reflex. Give examples to illustrate your answer.
Answer: Natural reflex: It is one in which no previous experience or learning is required. These reflexes are inborn i.e. inherited from the parents. Examples are 1. Blinking, coughing, sneezing as these are protective reflexes 2. Salivation, swallowing, peristalsis as it provides functional efficiency. 3. Dilation of the eyes pupil to look in the dark and vice versa. It is muscular movement. 4. Pushing along of swallowed food through the food canal. It is muscular movement.
Conditioned Reflex: It is one which develops during lifetime due to experience or learning. Examples are: 1. Watering of mouth (Salvination) at the sight of a tasty food. 2. Surfing the channels while watching the television. 3. Typing of a keyboard of a computer. 4. Playing a musical instrument.
Natural reflexes are hard-wired into our bodies for survival from the moment we are born. Conditioned reflexes are habits that become automatic only after we have done them many times.
Teacher's Tip: Natural = Born with it; Conditioned = Learned over time.
Exam Tip: Be sure to include multiple examples for both to show a broad understanding.

ADDITIONAL QUESTIONS

I. Multiple choice questions. Tick (✓) the correct choice:

1. Nervous system in humans consists of
1. brain and nerves
2. brain and spinal cord
3. brain, spinal cord and nerves
4. none of the above.
Answer: 3. brain, spinal cord and nerves
This trio works together to process information and direct the body's actions. The brain thinks, the spinal cord carries the message, and the nerves deliver it to the destination.
Teacher's Tip: Brain + Spinal Cord = Central; Nerves = Peripheral.
Exam Tip: If the question asks for the "Central" system only, then the answer would be brain and spinal cord.

2. Memory and intelligence are controlled by
1. cerebrum
2. medulla oblongata
3. cerebellum
4. spinal cord
Answer: 1. cerebrum
The cerebrum is the largest part of the brain and is responsible for high-level mental functions. It allows us to learn new languages, solve math problems, and remember our childhood.
Teacher's Tip: Cerebrum = "Thinking Cap."
Exam Tip: Remember that "intelligence" is always a function of the cerebral hemispheres.

3. Heartbeat and breathing are controlled by
1. cerebrum
2. spinal cord
3. cerebellum
4. medulla oblongata
Answer: 4. medulla oblongata
This part of the brain stem handles the automatic systems that keep the body alive. It functions constantly, whether you are awake, running, or deep in sleep.
Teacher's Tip: If you can't control it voluntarily, the Medulla is probably in charge.
Exam Tip: Always associate "vital involuntary functions" with the medulla oblongata.

II. Fill in the blanks:
1. Basic structural unit of the nervous system is the neuron.
2. Central nervous system consists of brain and spinal cord.
3. A neuron consists of cell body, dendrite and axon.
4. The neurons carrying impulses from the brain to the muscles are called motor or efferent neurons.
5. Peripheral nervous system consists of nerves.
6. The three main parts of the brain are cerebrum, cerebellum and medulla oblongata (brain stem).
These sentences summarize the fundamental organization and structure of our internal control system. Knowing these basic units helps explain how complex signals are transmitted throughout the body.
Teacher's Tip: "Efferent" means "Exiting" the brain (Motor nerves).
Exam Tip: Memorize the specific terms like "efferent" and "structural unit" as they are common fill-in-the-blank targets.

III. State whether the following statements are true (T) or false (F):
1. Each neuron consists of three parts called cell body, cyton and axon. False. Each neuron consists of three parts called cell body, dendrite and axon.
2. The largest part of the brain is the cerebrum. True.
3. Cerebellum maintains balance of the body, True.
4. There are 31 pairs of cranial nerves. False. There are 12 pairs of cranial nerves.
Correcting false statements is a great way to confirm you understand the specific details of biology. For example, knowing there are 12 cranial pairs helps distinguish them from the 31 pairs of spinal nerves.
Teacher's Tip: Cyton is another name for cell body, so the first statement was redundant, not accurate.
Exam Tip: Always count the specific number of nerve pairs (12 cranial, 31 spinal) carefully in your notes.

IV. Find the odd-one out, giving reasons:
Axon, cell body, dendrite, cerebellum
Answer: Cerebellum is the odd one out as it is apart of brain while rest three are parts of a neuron,
The first three terms describe the microscopic components of a single nerve cell. The cerebellum is a large, visible organ that makes up part of the entire brain.
Teacher's Tip: Look at the "Scale" of the objects (cell part vs. whole organ).
Exam Tip: When giving a reason, explain why the odd one is different and what the other three have in common.

V. Define the following:
1. Reflex arc: The path that an impulse takes in a reflex action is called a reflex arc.
2. Sensory neuron: The neurons which carry impulses from the body parts to the brain are called sensory or afferent neurons. For example, optic nerve of the eye.
3. Motor neuron: The neurons which carry impulses from the brain or spinal cord to the body parts are called motor or efferent neurons.
4. Neuron: A neuron or a nerve cell is the basic structural and functional unit of the nervous system.
These definitions help describe the physical circuitry that makes our bodies move and feel. The reflex arc is the specific "shortcut" that makes reflex actions so incredibly fast.
Teacher's Tip: "Afferent" = "Arriving" at the brain (Sensory).
Exam Tip: Include the example (Optic nerve) in your definition of a sensory neuron for a stronger answer.

VI. Answer the following:

Question 1: Describe the two parts of the nervous system.
Answer: The nervous system of human has two parts:
1. Central Nervous System (CNS): It consists of the brain and the spinal cord. The brain lies protected inside the skull while the spinal cord is protected within the vertebral column.
2. Peripheral Nervous System (PNS): It consists of nerves arising from the spinal cord (spinal nerves) and the brain (cranial nerves). These nerves link the central nervous system with the various body organs.
The CNS acts as the decision-maker, while the PNS acts as the delivery network for information. Together, they ensure every part of the body is connected to the control center.
Teacher's Tip: CNS = Central (Processing); PNS = Peripheral (Wiring).
Exam Tip: Be sure to mention where each part is "protected" (Skull and Vertebral Column).

Question 2: Draw a labelled diagram showing the structure of a neuron.
Answer: (Refer to the neuron diagram on Page 9 with Cyton, Nucleus, Dendrites, Axon, Myelin Sheath, and Axon Endings).
Diagrams of neurons show the clear "head" and "tail" structure of the cell. The myelin sheath is a fatty layer that helps the electrical signal travel much faster down the axon.
Teacher's Tip: Practice drawing the "star-shaped" cyton and the long "tail-like" axon.
Exam Tip: Always label the Nucleus and Myelin sheath as they are vital for cell function and signal speed.

Question 3: What are nerves? Mention the types of nerves found in humans.
Answer: A bundle of nerve fibres joined together as a tubular sheath that transmits impulses between brain or spinal cord and other body parts is called a nerve. The nerves constitute the peripheral nervous system. Nerves are of two types in humans:
1. Cranial nerves: They emerge from the brain. There are 12 pairs of cranial nerves. 2. Spinal nerves: They emerge from the spinal cord. There are 31 pairs of spinal nerves.
Nerves are like major cables that hold many smaller wires (axons) inside them. They are named based on whether they start at the brain or the spinal cord.
Teacher's Tip: Think of nerves as "Fiber-optic cables" for the body.
Exam Tip: Remember the numbers! 12 for the head (Cranial) and 31 for the body (Spinal).

Question 4: Explain the structure of brain.
Answer: The brain is the main control centre of the nervous system. It is enclosed within the bony shell of cranium. It consists of three main parts:
1. Cerebrum: It is the uppermost and largest part with many ridges and grooves. It is divided into right and left halves called cerebral hemispheres. It controls our thinking, reasoning, intelligence, memory and perception of pain, sound, touch, taste and smell.
2. Cerebellum: It is located under the cerebrum at the back of the head. It maintains balance of the body and coordinates muscular activity.
3. Brain stem (medulla oblongata): It joins the brain to the spinal cord. It controls the activity of internal organs i like heartbeat and breathing.
The brain is designed with specialized regions to handle different levels of complexity. The higher functions happen in the large cerebrum, while basic survival is handled in the brain stem.
Teacher's Tip: Cerebrum = Big brain (Thinking); Cerebellum = Little brain (Balance).
Exam Tip: Mention the "Cranium" as the protecting shell to provide a complete biological description.

Question 5: Compare the nervous system and the endocrine system.
Answer: Nervous system
1. Messages are sent through nerve fibres.
2. It consists of brain, spinal cord and nerves.
3. No hormones are secreted. Messages are sent as impulses.
4. Transmission of impulse is quick.
Endocrine system
1. Messages are sent through blood in the form of hormones.
2. It consists of endocrine glands.
3. Hormones secreted by glands regulate the body activities.
4. Transmission takes time.
This comparison highlights the difference between fast, targeted control (nervous) and slow, widespread control (endocrine). Both systems must work together to maintain a healthy internal balance in the body.
Teacher's Tip: Nervous = Fast/Specific; Endocrine = Slow/Generalized.
Exam Tip: Use a table format for "Comparison" questions to make your answer very easy for teachers to grade.

Question 6: Name three parts of brain.
Answer: Three parts of brain are cerebrum, cerebellum and medulla oblongata (brain stem).
Each of these three components has a unique role in either thinking, moving, or staying alive. They are protected together inside the cranial cavity of the skull.
Teacher's Tip: Memorize these three names as the "Big Three" of the brain.
Exam Tip: If the question is worth more than one mark, provide a very brief function for each part.

VOLUNTARY AND REFLEX ACTIONS, SENSE ORGANS

I. Multiple choice questions. Tick (✓) the correct choice:

1. Reflex actions occur under the control of
1. brain
2. medulla oblongata
3. spinal cord
4. cerebrum
Answer: 3. spinal cord
The spinal cord takes over during reflex actions to provide a faster response to dangerous stimuli. This avoids the delay of sending information all the way to the thinking part of the brain.
Teacher's Tip: Reflex = "Shortcut" through the spinal cord.
Exam Tip: Be careful! While the brain stem (medulla) controls involuntary actions like breathing, the *spinal cord* controls the protective reflex actions.

2. The coloured part of the eye is called
1. retina
2. iris
3. lens
4. pupil
Answer: 2. iris
The iris is a muscular ring that gives your eye its unique color, such as blue, brown, or green. Its main job is to adjust the size of the pupil to control how much light gets in.
Teacher's Tip: Think of the Iris as the "Colored Curtain" of the eye.
Exam Tip: Don't confuse the iris with the pupil; the pupil is just the hole in the center of the iris.

3. Pinna is a part of
1. inner ear
2. external ear
3. middle ear
4. tongue
Answer: 2. external ear
The pinna is the visible, outer part of the ear made of cartilage. It acts like a funnel to catch sound waves from the air and direct them into the ear canal.
Teacher's Tip: The pinna is the part you can actually touch on the outside of your head.
Exam Tip: Remember the ear has three compartments: external, middle, and inner.

4. The brown pigment melanin is present in ____ of skin.
1. Epidermis
2. Fat cells
3. Dermis
4. Hair follicles.
Answer: 1. Epidermis
Melanin is found in the outermost layer of the skin and determines our skin tone. It also protects our deeper tissues from being damaged by the sun's ultraviolet rays.
Teacher's Tip: Melanin = Natural Sunscreen.
Exam Tip: Specify that it is in the *inner* part of the epidermis specifically if the question gets more detailed.

II. Fill in the blanks:
1. Sense organs have special cells called receptors for picking up information and transmitting it to the nerves.
2. Outer protective layer of skin, called epidermis is made up of epithelial tissue.
3. The coloured part of eye is called iris.
These facts help explain how we perceive the world through our eyes, ears, and skin. Receptors are the specialized "receivers" that start the process of sensing everything around us.
Teacher's Tip: Receptors are the "Gateways" for information entering the body.
Exam Tip: Know that "epithelial tissue" refers to the type of tissue that forms coverings and linings.

III. State whether the following statements are true (T) or false (F):
1. The dermis of the skin is made up of epithelial cells. False. The epidermis of the skin is made up of epithelial cells.
2. The pigment melanin is present in inner layers of skin epidermis. True.
3. The sound waves from the outer ear are carried by the middle ear to the inner ear. True.
4. Cochlea is a part of middle car. False. Cochlea is a part of inner ear.
5. Retina is present on the outer surface of the eye. False. Retina is present on the inner surface of the eye.
Correcting these biological statements helps you learn the exact anatomy of our sense organs. For instance, knowing the cochlea is in the *inner ear* is key to understanding how we hear sounds.
Teacher's Tip: The "Dermis" is the thicker layer *under* the epidermis.
Exam Tip: Remember the order of sound travel: Outer Ear -> Middle Ear -> Inner Ear (Cochlea).

IV. Find the odd-one out, giving reasons:
Pinna, eardrum, cochlea, ear canal
Answer: Cochlea is the odd one out as it is a part of inner ear while the rest three are parts of outer ear.
While the other three components are responsible for gathering and channeling sound waves, the cochlea is responsible for actually converting them into nerve signals. It is located deep inside the head for protection.
Teacher's Tip: Cochlea is shaped like a snail shell!
Exam Tip: Grouping parts of the ear by location (external, middle, inner) is a great strategy for these questions.

V. Name the following:

Question 1: Five sense organs of human beings and the sensation perceived by each one.
Answer:
1. Eyes for sight.
2. Ears for hearing.
3. Nose for smelling.
4. Tongue for taste.
5. Skin for touch, heat, cold and pressure.
Our sense organs are our only windows to the outside world. They collect data about light, vibration, chemicals, and temperature to help us stay safe and interact with others.
Teacher's Tip: The skin is actually our largest sense organ!
Exam Tip: List all four sensations for "Skin" (touch, heat, cold, pressure) to give a complete answer.

Question 2: Flap like structure of outer ear.
Answer: Pinna.
The pinna is uniquely shaped to capture sound waves coming from different directions. Its fleshy, flexible structure is made of a material called cartilage.
Teacher's Tip: Some animals can even move their pinna to hear better!
Exam Tip: Mention that the pinna is part of the *external* ear.

VI. Answer the following:

Question 1: 1. Define voluntary and reflex actions. Give examples of each.
Answer: The actions which are controlled by the brain are called voluntary actions. For example, riding a bicycle, dancing or playing soccer. The actions which are under the control of the spinal cord are called reflex actions. For example, pulling away of hand from a hot object, blinking of eyes on dust getting into the eyes.
Voluntary actions require us to consciously think and decide to do something. Reflex actions are fast, automatic, and happen instantly to protect us from harm.
Teacher's Tip: Voluntary = "I want to do this"; Reflex = "My body did this automatically."
Exam Tip: Always associate voluntary actions with the *Cerebrum* (brain) and reflex actions with the *Spinal Cord*.

Question 2: Draw a labelled diagram to show the structure of skin.
Answer: (Refer to the Section of the skin diagram on Page 13 including Epithelial tissue, Sensory neuron, Hair follicle, Sebaceous gland, Epidermis, Dermis, and Sweat Gland).
The skin is more than just a cover; it contains complex glands, nerves, and layers. The sweat glands help cool the body, while sebaceous glands keep the skin and hair moisturized.
Teacher's Tip: Dermis is the "living layer" where the nerves and glands are found.
Exam Tip: Clearly show the two main layers (Epidermis and Dermis) in your diagram.

Question 3: Draw a labelled diagram of eye.
Answer: (Refer to the Eye diagram on Page 14 with Conjunctiva, Iris, Cornea, Pupil, Lens, Sclera, Retina, Blind Spot, and Optic Nerve).
The eye diagram shows how light passes through the clear cornea and lens to reach the retina. The blind spot is a tiny area on the retina where there are no receptor cells.
Teacher's Tip: Light enters through the "window" (Cornea) and hits the "screen" (Retina).
Exam Tip: Always include the Optic Nerve in your diagram as it is the link between the eye and brain.

Question 4: What are sense organs?
Answer: Sense organs are the parts of body which act as receptors that receive stimuli and send impulse to the brain. They help the body to know about the surroundings.
They act as biological detectors for change. Without them, we would have no way of knowing what is happening outside of our own bodies.
Teacher's Tip: Sense organs are the "Sensors" for the body's computer.
Exam Tip: Use the keyword "stimuli" and "receptor" in your definition for full marks.

Question 5: Give the functions of retina, pupil, and optic nerve.
Answer: Function of retina: It has light sensitive cells called rods and cones. Cones are responsible for coloured vision and observation when the light is strong. Rods are receptors for seeing in dim light. Retina has cells that convert the light falling on it into chemical signals that go to brain and get interpretted as image. Function of pupil: It controls the amount of light that enters the eye. It enlarges in dim light and becomes smaller in bright light. Function of optic nerve: It carries the message of sight from retina to the brain.
Each of these parts plays a distinct role in how we perceive light and color. The retina acts like the film in a camera, capturing the light patterns and turning them into data.
Teacher's Tip: Pupil = Aperture (Hole); Retina = Film/Sensor.
Exam Tip: Be sure to mention both rods and cones when describing the function of the retina.

Question 6: Differentiate between rods and cones.
Answer: Rods and cones are types of photoreceptors in the human eye.
Rods
1. It is responsible for detecting the dim light only with black and white.
2. Defects in rods cause night blindness.
Cones
1. It is responsible for detecting bright light with colors.
2. Defects in cones cause color blindness.
Rods are incredibly sensitive and help you navigate a dark room at night. Cones allow you to see the vibrant world in high detail and full color when there is plenty of light.
Teacher's Tip: Cones = Color (both start with C).
Exam Tip: Mention the specific eye defect (night blindness vs. color blindness) associated with each cell type.