Selina Textbook Solutions: Nervous System | Biology Class 7 ICSE PDF Download

 Page 1


Nervous System 
Synopsis — 
? The interaction of these activities of a living being as per the needs of the body 
internally or externally is called coordination. 
? Nervous coordination is brought about by the nervous system which is made up of 
the brain, spinal cord, nerves and the sense organs. 
? Chemical coordination is brought about through chemical messengers called 
hormones. 
? The nervous system is made up of special cells called nerve cells or neurons. 
? The end of the axon terminates in a number of branches called terminal branches. 
? The terminal branches of the axon of one neuron lie very close to the dendrites of 
another neuron. This point of contact is called a synapse. 
? A nerve is formed of a bundle of axons (nerve fibres) enclosed in a tubular 
medullary sheath. There are three kind of nerves as describe 
1. sensory nerve 
2. motor nerve 
3. mixed nerve. 
? The nervous sytem of human beings consists of the following three 
systems: 
1. The central nervous system 
2. The peripheral nervous system 
3. The autonomic nervous system 
? The brain has three main parts: 
1. The cerebrum 
2. The cerebellum, and 
3. The medulla oblongata 
? The main functions of the spinal cord are: 
1. To control reflexes below the neck. 
2. To conduct messages from the skin and muscles to the brain. 
3. To conduct commands from the brain to muscles of the trunk and limbs. 
? The autonomic nervous system consists of a pair of chain of nerves and ganglia 
found on either side of the backbone.  This system controls the involuntary 
activities of the internal organs. 
? Stimulus: Any change in the environment that usually results in change in the 
activity of the body. 
? Response: The activity of the body in response to a received stimulus. 
? Impulse: A wave of electrical disturbance that runs through the nerves. 
? Receptors : These are sense organs which receives the stimulus. 
? Effector: Any muscle or gland where the response occurs. 
 
 
Page 2


Nervous System 
Synopsis — 
? The interaction of these activities of a living being as per the needs of the body 
internally or externally is called coordination. 
? Nervous coordination is brought about by the nervous system which is made up of 
the brain, spinal cord, nerves and the sense organs. 
? Chemical coordination is brought about through chemical messengers called 
hormones. 
? The nervous system is made up of special cells called nerve cells or neurons. 
? The end of the axon terminates in a number of branches called terminal branches. 
? The terminal branches of the axon of one neuron lie very close to the dendrites of 
another neuron. This point of contact is called a synapse. 
? A nerve is formed of a bundle of axons (nerve fibres) enclosed in a tubular 
medullary sheath. There are three kind of nerves as describe 
1. sensory nerve 
2. motor nerve 
3. mixed nerve. 
? The nervous sytem of human beings consists of the following three 
systems: 
1. The central nervous system 
2. The peripheral nervous system 
3. The autonomic nervous system 
? The brain has three main parts: 
1. The cerebrum 
2. The cerebellum, and 
3. The medulla oblongata 
? The main functions of the spinal cord are: 
1. To control reflexes below the neck. 
2. To conduct messages from the skin and muscles to the brain. 
3. To conduct commands from the brain to muscles of the trunk and limbs. 
? The autonomic nervous system consists of a pair of chain of nerves and ganglia 
found on either side of the backbone.  This system controls the involuntary 
activities of the internal organs. 
? Stimulus: Any change in the environment that usually results in change in the 
activity of the body. 
? Response: The activity of the body in response to a received stimulus. 
? Impulse: A wave of electrical disturbance that runs through the nerves. 
? Receptors : These are sense organs which receives the stimulus. 
? Effector: Any muscle or gland where the response occurs. 
 
 
Review Questions 
Multiple Choice Questions: 
1. Put a tick mark ( ?) against the correct alternative in the following statements: 
 
(a) Medulla oblongata controls 
(i) Smelling 
(ii) Beating of heart and respiratory movement 
(iii) Intelligence and will power 
(iv) Balancing the body 
(b) Spinal cord is an extention of: 
(i) Cerebellum 
(ii) Cerebrum 
(iii) Vertebral column 
(iv) Medulla oblongata 
(c) Body posture is mantained by: 
(i) Cerebellum 
(ii) Cerebrum 
(iii) Medulla oblongata 
(iv) Spinal cord 
Short Answer Questions: 
1. 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: beathing: medulla oblongata 
Balance: cerebellum:: reasoning: cerebrum 
2. (a) Name three major divisions of the human nervous system. 
Answer: 
1. The central nervous system (brain and spinal cord) 
2. The peripheral nervous system 
3. The autonomic nervous system 
(b) Name the three main parts of human brain. 
 
Page 3


Nervous System 
Synopsis — 
? The interaction of these activities of a living being as per the needs of the body 
internally or externally is called coordination. 
? Nervous coordination is brought about by the nervous system which is made up of 
the brain, spinal cord, nerves and the sense organs. 
? Chemical coordination is brought about through chemical messengers called 
hormones. 
? The nervous system is made up of special cells called nerve cells or neurons. 
? The end of the axon terminates in a number of branches called terminal branches. 
? The terminal branches of the axon of one neuron lie very close to the dendrites of 
another neuron. This point of contact is called a synapse. 
? A nerve is formed of a bundle of axons (nerve fibres) enclosed in a tubular 
medullary sheath. There are three kind of nerves as describe 
1. sensory nerve 
2. motor nerve 
3. mixed nerve. 
? The nervous sytem of human beings consists of the following three 
systems: 
1. The central nervous system 
2. The peripheral nervous system 
3. The autonomic nervous system 
? The brain has three main parts: 
1. The cerebrum 
2. The cerebellum, and 
3. The medulla oblongata 
? The main functions of the spinal cord are: 
1. To control reflexes below the neck. 
2. To conduct messages from the skin and muscles to the brain. 
3. To conduct commands from the brain to muscles of the trunk and limbs. 
? The autonomic nervous system consists of a pair of chain of nerves and ganglia 
found on either side of the backbone.  This system controls the involuntary 
activities of the internal organs. 
? Stimulus: Any change in the environment that usually results in change in the 
activity of the body. 
? Response: The activity of the body in response to a received stimulus. 
? Impulse: A wave of electrical disturbance that runs through the nerves. 
? Receptors : These are sense organs which receives the stimulus. 
? Effector: Any muscle or gland where the response occurs. 
 
 
Review Questions 
Multiple Choice Questions: 
1. Put a tick mark ( ?) against the correct alternative in the following statements: 
 
(a) Medulla oblongata controls 
(i) Smelling 
(ii) Beating of heart and respiratory movement 
(iii) Intelligence and will power 
(iv) Balancing the body 
(b) Spinal cord is an extention of: 
(i) Cerebellum 
(ii) Cerebrum 
(iii) Vertebral column 
(iv) Medulla oblongata 
(c) Body posture is mantained by: 
(i) Cerebellum 
(ii) Cerebrum 
(iii) Medulla oblongata 
(iv) Spinal cord 
Short Answer Questions: 
1. 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: beathing: medulla oblongata 
Balance: cerebellum:: reasoning: cerebrum 
2. (a) Name three major divisions of the human nervous system. 
Answer: 
1. The central nervous system (brain and spinal cord) 
2. The peripheral nervous system 
3. The autonomic nervous system 
(b) Name the three main parts of human brain. 
 
Answer: 
1. Cerebrum 
2. Cerebellum 
3. Medulla oblongata 
3. Given here is the diagram of a neuron. Name the parts numbered 1-6. 
 
Answer: 
1. dendrite 
2. dendrite (Terminal Arborization) 
3. nucleus 
4. axon (Nerve fibre) 
5. cell Body (cyton) 
6. node of ranvier 
7. sheath 
 
 
 
 
 
 
Page 4


Nervous System 
Synopsis — 
? The interaction of these activities of a living being as per the needs of the body 
internally or externally is called coordination. 
? Nervous coordination is brought about by the nervous system which is made up of 
the brain, spinal cord, nerves and the sense organs. 
? Chemical coordination is brought about through chemical messengers called 
hormones. 
? The nervous system is made up of special cells called nerve cells or neurons. 
? The end of the axon terminates in a number of branches called terminal branches. 
? The terminal branches of the axon of one neuron lie very close to the dendrites of 
another neuron. This point of contact is called a synapse. 
? A nerve is formed of a bundle of axons (nerve fibres) enclosed in a tubular 
medullary sheath. There are three kind of nerves as describe 
1. sensory nerve 
2. motor nerve 
3. mixed nerve. 
? The nervous sytem of human beings consists of the following three 
systems: 
1. The central nervous system 
2. The peripheral nervous system 
3. The autonomic nervous system 
? The brain has three main parts: 
1. The cerebrum 
2. The cerebellum, and 
3. The medulla oblongata 
? The main functions of the spinal cord are: 
1. To control reflexes below the neck. 
2. To conduct messages from the skin and muscles to the brain. 
3. To conduct commands from the brain to muscles of the trunk and limbs. 
? The autonomic nervous system consists of a pair of chain of nerves and ganglia 
found on either side of the backbone.  This system controls the involuntary 
activities of the internal organs. 
? Stimulus: Any change in the environment that usually results in change in the 
activity of the body. 
? Response: The activity of the body in response to a received stimulus. 
? Impulse: A wave of electrical disturbance that runs through the nerves. 
? Receptors : These are sense organs which receives the stimulus. 
? Effector: Any muscle or gland where the response occurs. 
 
 
Review Questions 
Multiple Choice Questions: 
1. Put a tick mark ( ?) against the correct alternative in the following statements: 
 
(a) Medulla oblongata controls 
(i) Smelling 
(ii) Beating of heart and respiratory movement 
(iii) Intelligence and will power 
(iv) Balancing the body 
(b) Spinal cord is an extention of: 
(i) Cerebellum 
(ii) Cerebrum 
(iii) Vertebral column 
(iv) Medulla oblongata 
(c) Body posture is mantained by: 
(i) Cerebellum 
(ii) Cerebrum 
(iii) Medulla oblongata 
(iv) Spinal cord 
Short Answer Questions: 
1. 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: beathing: medulla oblongata 
Balance: cerebellum:: reasoning: cerebrum 
2. (a) Name three major divisions of the human nervous system. 
Answer: 
1. The central nervous system (brain and spinal cord) 
2. The peripheral nervous system 
3. The autonomic nervous system 
(b) Name the three main parts of human brain. 
 
Answer: 
1. Cerebrum 
2. Cerebellum 
3. Medulla oblongata 
3. Given here is the diagram of a neuron. Name the parts numbered 1-6. 
 
Answer: 
1. dendrite 
2. dendrite (Terminal Arborization) 
3. nucleus 
4. axon (Nerve fibre) 
5. cell Body (cyton) 
6. node of ranvier 
7. sheath 
 
 
 
 
 
 
Long answer questions 
Question 1. 
With the help of a suitable diagram describe the structure 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 dendrites ?Cell body ? Axon ? Muscles or  glands 
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 
Page 5


Nervous System 
Synopsis — 
? The interaction of these activities of a living being as per the needs of the body 
internally or externally is called coordination. 
? Nervous coordination is brought about by the nervous system which is made up of 
the brain, spinal cord, nerves and the sense organs. 
? Chemical coordination is brought about through chemical messengers called 
hormones. 
? The nervous system is made up of special cells called nerve cells or neurons. 
? The end of the axon terminates in a number of branches called terminal branches. 
? The terminal branches of the axon of one neuron lie very close to the dendrites of 
another neuron. This point of contact is called a synapse. 
? A nerve is formed of a bundle of axons (nerve fibres) enclosed in a tubular 
medullary sheath. There are three kind of nerves as describe 
1. sensory nerve 
2. motor nerve 
3. mixed nerve. 
? The nervous sytem of human beings consists of the following three 
systems: 
1. The central nervous system 
2. The peripheral nervous system 
3. The autonomic nervous system 
? The brain has three main parts: 
1. The cerebrum 
2. The cerebellum, and 
3. The medulla oblongata 
? The main functions of the spinal cord are: 
1. To control reflexes below the neck. 
2. To conduct messages from the skin and muscles to the brain. 
3. To conduct commands from the brain to muscles of the trunk and limbs. 
? The autonomic nervous system consists of a pair of chain of nerves and ganglia 
found on either side of the backbone.  This system controls the involuntary 
activities of the internal organs. 
? Stimulus: Any change in the environment that usually results in change in the 
activity of the body. 
? Response: The activity of the body in response to a received stimulus. 
? Impulse: A wave of electrical disturbance that runs through the nerves. 
? Receptors : These are sense organs which receives the stimulus. 
? Effector: Any muscle or gland where the response occurs. 
 
 
Review Questions 
Multiple Choice Questions: 
1. Put a tick mark ( ?) against the correct alternative in the following statements: 
 
(a) Medulla oblongata controls 
(i) Smelling 
(ii) Beating of heart and respiratory movement 
(iii) Intelligence and will power 
(iv) Balancing the body 
(b) Spinal cord is an extention of: 
(i) Cerebellum 
(ii) Cerebrum 
(iii) Vertebral column 
(iv) Medulla oblongata 
(c) Body posture is mantained by: 
(i) Cerebellum 
(ii) Cerebrum 
(iii) Medulla oblongata 
(iv) Spinal cord 
Short Answer Questions: 
1. 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: beathing: medulla oblongata 
Balance: cerebellum:: reasoning: cerebrum 
2. (a) Name three major divisions of the human nervous system. 
Answer: 
1. The central nervous system (brain and spinal cord) 
2. The peripheral nervous system 
3. The autonomic nervous system 
(b) Name the three main parts of human brain. 
 
Answer: 
1. Cerebrum 
2. Cerebellum 
3. Medulla oblongata 
3. Given here is the diagram of a neuron. Name the parts numbered 1-6. 
 
Answer: 
1. dendrite 
2. dendrite (Terminal Arborization) 
3. nucleus 
4. axon (Nerve fibre) 
5. cell Body (cyton) 
6. node of ranvier 
7. sheath 
 
 
 
 
 
 
Long answer questions 
Question 1. 
With the help of a suitable diagram describe the structure 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 dendrites ?Cell body ? Axon ? Muscles or  glands 
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 nine 
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. 
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. 
Question 4. 
Describe three kinds of nerves, giving 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.