Check your progress
Question 1
The reaction of an organism to a stimulus is called a ............... .
Answer
The reaction of an organism to a stimulus is called a response.
Question 2
The basic structural unit of the nervous system is called a ............... .
Answer
The basic structural unit of the nervous system is called a neuron.
Question 3
............... nourishes the brain and absorbs shocks.
Answer
Cerebrospinal fluid nourishes the brain and absorbs shocks.
Question 4
............... is the largest part of the brain.
Answer
Cerebrum is the largest part of the brain.
Question 5
............... maintains the balance of the body.
Answer
Cerebellum maintains the balance of the body.
Tick the most appropriate answer
Question 1
Short fibres extending from the cell body of a nerve cell are called
- dendrons
- axons
- dendrites
- ganglia
Answer
dendrons
Reason — Short fibres extending from the cell body of a nerve cell are called dendrons which further divide to form dendrites.
Question 2
The message that travels along a nerve is called
- stimulus
- response
- sensation
- impulse
Answer
impulse
Reason — Messages along the neuron travel in the form of a wave of chemical disturbance. This chemical disturbance is called an impulse.
Question 3
Breathing and heartbeat are controlled by the
- cerebellum
- cerebrum
- medulla oblongata
- nerve cells
Answer
medulla oblongata
Reason — Medulla oblongata controls involuntary movements like breathing and heartbeat.
Question 4
This is the centre for intelligence and memory
- cerebellum
- cerebrum
- medulla oblongata
- spinal cord
Answer
cerebrum
Reason — Centre for intelligence and memory is cerebrum.
Question 5
This part of the brain maintains the balance of the body.
- cerebellum
- cerebrum
- medulla oblongata
- spinal cord
Answer
cerebellum
Reason — Cerebellum maintains the balance of the body.
Fill in the blanks
Question 1
............... is the basic structural unit of the nervous system.
Answer
Neuron is the basic structural unit of the nervous system.
Question 2
A single long fibre extending from the cell body of a neuron is called ............... .
Answer
A single long fibre extending from the cell body of a neuron is called axon.
Question 3
The central nervous system comprises ............... and ............... .
Answer
The central nervous system comprises brain and spinal cord.
Question 4
The ............... nervous system comprises the nerves arising from the brain and spinal cord.
Answer
The peripheral nervous system comprises the nerves arising from the brain and spinal cord.
Question 5
The brain is enveloped by three membranes called ............... .
Answer
The brain is enveloped by three membranes called meninges.
Match the following
Question 1
| Sl. No. | Column A | Column B |
|---|---|---|
| 1. | Spinal cord | body balance |
| 2. | Cerebrum | reflex action |
| 3. | Cerebellum | intelligence and memory |
| 4. | Medulla oblongata | junction of two neurons |
| 5. | Synapse | carries messages to the brain |
| 6. | Sensory nerve | heartbeat |
Answer
| Sl. No. | Column A | Column B |
|---|---|---|
| 1. | Spinal cord | reflex action |
| 2. | Cerebrum | intelligence and memory |
| 3. | Cerebellum | body balance |
| 4. | Medulla oblongata | heartbeat |
| 5. | Synapse | junction of two neurons |
| 6. | Sensory nerve | carries messages to the brain |
Write true of False. Correct the false statements.
Question 1
Each nerve cell consists of a cell body, many short fibres and a long fibre.
Answer
False
Corrected statement — Each nerve cell consists of a cell body, many short fibres which further divide into dendrites and a long fibre.
Question 2
Mixed nerves carry impulses from the sense organs to the spinal cord.
Answer
False
Corrected statement — Mixed nerves contain both sensory and motor fibres hence they perform the function of both sensory nerves and motor nerves.
Question 3
The cerebellum is the largest part of the brain.
Answer
False
Corrected statement — The cerebrum is the largest part of the brain.
Question 4
Thinking, reasoning and memory are controlled by the medulla oblongata.
Answer
False
Corrected statement — Thinking, reasoning and memory are controlled by the cerebrum.
Question 5
The cerebrum controls the balance of the body.
Answer
False
Corrected statement — The cerebellum controls the balance of the body.
Differentiate between
Question 1
neuron and nerve
Answer
| Sl. No. | Neuron | Nerve |
|---|---|---|
| 1. | A neuron is a specialized cell for receiving messages from one part of the body and conducting them to the other parts. | Nerve cells when joined end to end form a nerve. |
| 2. | Each nerve cell consists of a cell body (cyton), many short fibres (dendrons) which further divide into dendrites and a long fibre (axon). | A nerve consists of a cord-like structure with a number of nerve fibres bundled together. |
Question 2
sensory nerves and mixed nerves.
Answer
| Sl. No. | Sensory Nerves | Mixed Nerves |
|---|---|---|
| 1. | Sensory nerves are the nerves that carry messages from the sense organs to either the spinal cord or the brain. | Mixed nerves perform the function of both sensory nerves and motor nerves. They transmit messages from the central nervous system to the muscles of the body. |
| 2. | They contain only sensory fibres. | They contain sensory fibres as well as motor fibres. |
| 3. | For example, the optic nerve that sends messages from the eye to the brain is a sensory nerve. | For example, the nerve that transmits messages to the tongue is a mixed nerve. |
Question 3
central nervous system and peripheral nervous system
Answer
| Sl. No. | Central Nervous System | Peripheral Nervous System |
|---|---|---|
| 1. | It consists of the brain and the spinal cord. | It comprises of the nerves arising from brain and the spinal cord. |
| 2. | It is the main part of nervous system which stores information and processes it. | It participates in receiving information and stimulus response |
Question 4
cerebrum and cerebellum
Answer
| Sl. No. | Cerebrum | Cerebellum |
|---|---|---|
| 1. | It is the uppermost, largest and the most prominent part of the brain. | It is a small, egg-shaped lobe located at the base under the cerebrum. |
| 2. | It is highly convoluted in appearance with ridges and grooves. | It does not have convolutions, but has many furrows. |
| 3. | It controls mental activities such as thinking and reasoning, memory, intelligence and perception of taste, pain and touch etc. | It coordinates the movement of voluntary muscles and maintains the balance of the body. |
Find the odd one out. Give reasons for your choice.
Question 1
dendron, cyton, cerebrum, dendrite, axon
Answer
cerebrum
Reason — Cerebrum is the part of brain while others are part of nerve cell or neuron.
Question 2
thinking, reasoning, memory, body balance
Answer
body balance
Reason — Body balance is the function of cerebellum while thinking, reasoning and memory are functions of cerebrum
Answer the following in short
Question 1
What is a stimulus?
Answer
Any sudden change in the environment of an organism that causes a reaction in that organism is called a stimulus.
Question 2
Name the three important parts of the brain.
Answer
The three important parts of the brain are:
- Cerebrum
- Cerebellum
- Medulla oblongata
Question 3
Write the function of the cerebrospinal fluid.
Answer
The functions of the cerebrospinal fluid are:
- Nourishes the brain.
- Protects it by absorbing shocks.
Question 4
What is a reflex action?
Answer
Reflex action is a quick, automatic response to a stimulus, without the involvement of the brain.
Answer the following in detail
Question 1
Explain the structure of a nerve cell with the help of a diagram.
Answer
A nerve cell or neuron is the basic structural unit of the nervous system. It has three parts — cell body, axon and dendrites.
- The cell body called cyton contains the nucleus.
- Many short fibres called dendrons arise from the cell. They further divide to form dendrites. Dendrites receive messages from other neurons.
- A single, long fibre called axon extends from the other side of the cell body. It is covered by a sheath called myelin sheath.
Below diagram shows the structure of a neuron:
Question 2
Distinguish between motor, sensory and mixed nerves with respect to their functions.
Answer
| Motor nerves | Sensory nerves | Mixed nerves |
|---|---|---|
| It carries messages in the form of responses from the brain or spinal cord to other parts of the body such as muscles and glands. | It carries messages (impulses) from the sense organs to either the spinal cord or the brain. | It performs the function of both motor and sensory nerves. They transmit electrical impulses from the central nervous system to the muscles of the body. |
Question 3
Describe the central nervous system along with its parts and functions.
Answer
The central nervous system consists of the brain and the spinal cord. It is the control centre for all body functions. It is the site for all information processing in the body. It is responsible for processing every sensation and thought a human being experiences. It has two parts — Brain and Spinal Cord.
- Brain — The Brain is the main control centre of the nervous system situated in the cranium of the skull. It controls our thinking, feelings, movement and senses. It has three parts — Cerebrum, Cerebellum and Medulla oblongata.
- Cerebrum — The cerebrum is the uppermost, largest and the most prominent part of the brain. It is responsible for the sensation of pain, temperature, touch, sight, sound, taste and smell. It also controls mental activities such as memory, intelligence, thinking and reasoning.
- Cerebellum — The cerebellum is a small, egg-shaped lobe located at the base under the cerebrum. It helps in the muscle coordination and balance of the body.
- Medulla oblongata — The Medulla oblongata is the lowermost part of the brain located at the base of the skull. It controls breathing, heartbeat, coughing, sneezing and other involuntary functions.
- Spinal cord — The spinal cord is the continuation of the medulla oblongata of the brain. It is like a cord that emerges from a hole at the base of the skull and runs through the vertebral column. The spinal cord conducts reflexes below the neck. It conducts sensory impulses from the skin and muscles to the brain. It conducts motor responses from the brain to the muscles of the trunk and limbs.
Question 4
Explain how messages reach the brain.
Answer
The peripheral nervous system transmits messages to and from the sense organs and is responsible for voluntary actions such as cycling, swimming and so on. Messages enter the spinal cord from all parts of the body and reach the brain, which sends back the messages to various body parts through the spinal cord.
Label the parts
Question 1
What does this picture show? Label the parts.
Answer
This picture shows 'Synapse between neurons'. The labelled parts are shown below:
Think and answer
Question 1
When you step on a needle, you immediately withdraw your foot. Which part of the nervous system makes this happen?
Answer
Spinal cord is responsible for this action. Immediately withdrawing our foot after stepping on a needle is a reflex action which happens without thinking i.e., the brain is not involved. Reflex actions are controlled by spinal cord.