The Nervous System

Multiple Choice Type

(Select the most appropriate option in each case)

Question 1

The insulating sheath covering the axon is called

1. Plasmalemma
2. Neurilemma ✓
3. Dura mater
4. Pia mater

Question 2

Which one of the following pairs of brain part and its function is not correctly matched?

1. Cerebrum — memory
2. Cerebellum — balance of body
3. Medulla oblongata — controls activities of internal organs
4. Pons — consciousness ✓

Question 3

A mixed nerve is one which

1. Carries sensation from 2 or more different sense organs
2. Contains both sensory and motor fibres ✓
3. Has a common root but branches into two or more nerves to different organs
4. Has two or more roots from different parts of brain.

Question 4

Reflex action is controlled by

1. Brain
2. Spinal cord ✓
3. Autonomic
4. Peripheral nervous system

Question 5

Which one of the following is responsible for controlling the body temperature?

1. Liver
2. Lung
3. Hypothalamus ✓
4. Spinal cord

Question 6

Which of the following is absent in a neuron?

1. Ribosome
2. Centrosome ✓
3. Chromosome
4. Lysosome

Question 7

The basic structural and functional unit of brain is

1. Nephron
2. Nerve
3. Spinal cord
4. Neuron ✓

Very Short Answer Type

Question 1(a)

Name the following:

The fluid that is present inside and outside the brain.

Answer

Cerebrospinal fluid

Question 1(b)

Name the following:

The junction between two nerve cells.

Answer

Synapse

Question 1(c)

Name the following:

The part of the brain which is concerned with memory.

Answer

Cerebrum

Question 1(d)

Name the following:

The central space of the brain.

Answer

Ventricle

Question 2

Note the relationship between the first two words and suggest the suitable word/words for the fourth place.

(a) Stimulus : Receptor :: Impulse : _________

(b) Cerebrum : Diencephalon :: Cerebellum : _________

(c) Receptor : Sensory nerve :: Motor nerve : _________

(d) Axons : Nerve :: Cytons : _________

(e) Cerebrum : Corpus callosum :: Cerebellum : _________.

Answer

(a) Stimulus : Receptor :: Impulse : Effector

(b) Cerebrum : Diencephalon :: Cerebellum : Medulla oblongata

(c) Receptor : Sensory nerve :: Motor nerve : Effector

(d) Axons : Nerve :: Cytons : Nerve cells

(e) Cerebrum : Corpus callosum :: Cerebellum : Pons

Question 3

Complete the following statements by choosing the correct alternative from the choices given in brackets:

(a) The dorsal root ganglion of the spinal cord contains cell bodies of (motor/ sensory/ intermediate) neurons.

(b) Cerebellum is the part of the brain which is responsible for

(i) Conducting reflexes in the body

(ii) Maintaining posture and equilibrium

(iii) Controlling thinking, memory and reasoning.

Answer

(a) Sensory neurons.

(b) Maintaining posture and equilibrium.

Short Answer Type

Question 1

Mention where in human body are the following located and state their main functions:

(a) Corpus callosum

(b) Central canal

Answer

(a) Corpus Callosum — Corpus callosum ("hard body") is a sheet of fibres connecting the two cerebral hemispheres. It is located in the forebrain. It connects two cerebral hemispheres and transfers information from one hemisphere to other.

(b) Central Canal — It is located in centre of the spinal cord. It is in continuation with the cavities of the brain. It is filled with cerebrospinal fluid and acts as shock proof cushion. In addition, it also helps in exchange of materials with neurons.

Question 2

State whether the following statements are true (T) or false (F).

(a) The main component of the white matter of the brain is perikaryon.

Answer

False

(b) The arachnoid layer fits closely inside the pia mater.

Answer

False

(c) A double chain of ganglia, one on each side of the nerve cord belongs to the spinal cord.

Answer

True

(d) Dura mater is the outermost layer of the meninges.

Answer

True

Question 3

State whether the following are simple reflexes, conditioned reflexes or neither of the two.

(i) Sneezing........................

(ii) Blushing........................

(iii) Contraction of eye pupil....................

(iv) Lifting up a book........................

(v) Knitting without looking.....................

(vi) Sudden application of brakes of the cycle on sighting an obstacle in front...................

Answer

Question 4

State the functions of the following:

(a) Association neuron

(b) Myelin sheath

(c) Medullary sheath

(d) Cerebrospinal fluid

Answer

(a) Association neuron — Association neurons carry impulses from the motor neuron to the Central Nervous System (CNS) or a nerve cell found entirely within the central nervous system. It acts as a connecting neuron and interconnects the sensory and motor neurons.

(b) Myelin sheath — It acts like an insulation and prevents mixing of impulses in the adjacent axons.

(c) Medullary sheath — It provides insulation and prevents mixing of impulses in the adjacent axons.

(d) Cerebrospinal fluid — It acts like a cushion and protects the brain from shocks.

Question 5

Rearrange the following in correct sequence pertaining to what is given within brackets at the end.

(a) Effector — Sensory neuron — Receptor — Motor neuron — Stimulus — Central nervous system — Response (Reflex arc)

(b) Repolarization — Depolarization — Resting (polarsied) (during conduction of nerve impulse through a nerve fibre)

(c) Axon endings — Dendrites — Axon — Perikaryon — Dendron (Neuron structure)

(d) Diencephalon — Cerebellum — Medulla oblongata — Pons — Cerebrum — mid brain (sequence of parts of human brain).

Answer

(a) Stimulus — receptor — sensory neuron — central nervous system — motor neuron — effector — response.

(b) Resting — depolarization — repolarization.

(c) Dendrites — Dendron — perikaryon — nucleus — axon — axon endings.

(d) Cerebrum — diencephalon — mid-brain — cerebellum — pons — medulla oblongata.

Question 6

Name the following:

(a) Three types of neurons

(b) Three types of nerves

(c) Three main parts of the neuron

(d) Two major divisions of the nervous system

(e) Three layers of the meninges

(f) Three main parts of the brain

(g) Two parts of the autonomic nervous system

(h) Two types of reflexes.

Answer

(a) Three types of neurons —

1. Sensory neurons
2. Motor neurons
3. Association neurons

(b) Three types of nerves —

1. Sensory nerves
2. Motor nerves
3. Mixed nerves

(c) Three main parts of the neuron —

1. Cyton
2. Dendrites
3. Axon

(d) Two major divisions of the nervous system —

1. Central nervous system
2. Peripheral nervous system

(e) Three layers of the meninges —

1. Dura mater
2. Arachnoid
3. Pia mater

(f) Three main parts of the brain —

1. Cerebrum
2. Cerebellum
3. Medulla oblongata

(g) Two parts of the autonomic nervous system —

1. Sympathetic nervous system
2. Parasympathetic nervous system

(h) Two types of reflexes —

1. Natural (inborn) reflex
2. Conditioned (acquired) reflex.

Question 7

Write the full forms of the following abbreviations:

(a) CSF

(b) CNS

(c) PNS

(d) ANS

Answer

(a) CSF — Cerebrospinal fluid

(b) CNS — Central Nervous System

(c) PNS — Peripheral Nervous System

(d) ANS — Autonomic Nervous System

Descriptive Type

Question 1

Define the following terms:

(a) Neuron

(b) Nerve

(c) Stimulus

(d) Synaptic cleft

(e) Reflex action

(f) Corpus callosum

Answer

(a) Neuron — (nerve cells) are the fundamental units of the nervous system specialized to transmit information in the form of electrical impulses to different parts of the body.

(b) Nerve — Nerve is a bundle of nerve fibres (axons) of separate neurons, enclosed in a tubular sheath.

(c) Stimulus — An agent or the sudden change of the external or internal environment that results in a change in an organism or any of its body parts is called a stimulus.

(d) Synaptic cleft — The gaps between the axon terminals and the dendrites of another one or more neurons are called synaptic clefts.

(e) Reflex action — Reflex action is an automatic or quick or immediate involuntary action in the body brought about by a stimulus.

(f) Corpus callosum — Corpus callosum is a sheet of fibres connecting the two cerebral hemispheres.

Question 2

Distinguish between the following pairs:

(a) Cerebrum and cerebellum (function)

(b) Sympathetic nervous system and parasympathetic nervous system (location and role)

(c) Sensory nerve and motor nerve (direction of impulse carried)

(d) Cerebrum and spinal cord (arrangement of cytons and axons of neurons)

(e) Cranial nerves and spinal nerves (number in pairs)

(f) Nerve impulse and flow of electricity (transmission and speed)

(g) Medulla oblongata and cerebellum (function)

Answer

(a) Difference between cerebrum and cerebellum (function)

(b) Difference between sympathetic nervous system and parasympathetic nervous system (location and role)

(c) Difference between sensory nerve and motor nerve (direction of impulse carried)

d) Difference between cerebrum and spinal cord (arrangement of cytons and axons of neurons)

(e) Difference between cranial nerves and spinal nerves (number in pairs)

(f) Difference between nerve impulse and flow of electricity (transmission and speed)

(g) Difference between medulla oblongata and cerebellum (function)

Question 3

While watching a scary movie, mention its effects on the following organs by the autonomous nervous system, in the table given below: (one has been done for you as an example).

Answer

Question 4

Give reason:

(a) The brain and the spinal cord are referred to as the central nervous system.

(b) Neurotransmitters are broken down by an enzyme just after passing an impulse from one neuron to the other.

Answer

(a) Central nervous system includes the brain and the spinal cord contained within the vertebral column. They have an important role to play because all bodily activities are controlled by them. A stimulus from any part of the body is always carried to the brain or spinal cord for the correct response. A response to a stimulus is also generated in the central nervous system. Therefore, the brain and the spinal cord are called the central nervous system.

(b) Neurotransmitters are broken down by an enzyme just after passing an impulse from one neuron to the other to make the synapse ready for the next transmission of impulse.

Question 5

What are the advantages of having a nervous system?

Answer

The advantages of having a nervous system are as follows:

1. Keeps us informed about the outside world through sense organs.
2. Enables us to remember, think and reason out.
3. Controls and harmonizes all voluntary muscular activities such as running, holding, writing.
4. Regulates involuntary activities such as breathing, beating of the heart without our thinking about them.

Question 6

Draw a labelled diagram of a myelinated neuron.

Answer

Labelled diagram of a myelinated neuron is shown below:

Question 7

What is the difference between reflex action and voluntary action?

Answer

Structured / Application / Skill Type

Question 1

Two hungry boys (A and B) enter a restaurant and see the menu. Boy B starts salivating but not A. Explain the reason for this difference.

Answer

Salivation can occur as a conditioned reflex simply at the sight or by the smell of a familiar tasty food. This means that if we have not eaten that food earlier, the response will not occur. Boy B starts salivating because he has tasted the foods in the menu earlier, so his brain remembers the tastes of those foods and salivation occurs as a conditioned reflex for him. On the other hand, boy A has not tasted those foods earlier, his brain does not know the taste of those foods hence no conditioned reflex occurs for him.

Question 2

The diagram alongside shows a section of the human brain and its associated parts. Answer the questions that follow:

(a) Name the parts labelled 1, 2, 3 and 4.

(b) Name the protective membranous covering of the brain. Also mention its three layers.

(c) Name the basic unit of the brain.

(d) Write the important role of the part mentioned as 2.

Answer

(a) The parts labelled 1-4 are:

• 1 → Cerebrum
• 2 → Cerebellum
• 3 → Pons
• 4 → Medulla oblongata

(b) The brain is protected by 3 membranous coverings called Meninges. The three layers of meninges are:

1. Dura mater
2. Arachnoid
3. Pia mater.

(c) Neuron/nerve cell.

(d) Cerebellum (part 2) is concerned with maintaining the balance of the body and the coordination of muscular activities.

Question 3

Given below are a few situations. What effective change will occur in the organ/body part mentioned and which part (sympathetic or parasympathetic) of the autonomic nervous system brings it about?

Answer

Question 4

Given below is the partially incomplete scheme of the components of peripheral nervous system. Fill up the blanks numbered (1) - (12).

Answer

1 - Central Nervous System

2 - Autonomic

3 - 12

4 - spinal

5 - 31

6 - neck

7 - waist

8 - dilates

9 - constricts

10 - liver

11 - neck

12 - sacrum