Concise Biology Part II - Selina Solutions for Class Biology ICSE Chapter 10: The Nervous System

(b) neurolemma

(d) Pons - consciousness

(b) Contains both sensory and motor fibres

(b) Spinal cord

(c) Hypothalamus

(b) Centrosome

(d) Neuron

(a) Cerebrospinal fluid

(b) Synapse

(c) Cerebrum

(d) Ventricle

(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

(a) Sensory

(b) Maintaining posture and equilibrium

(a) Corpus Callosum - It is located 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.

(a) False

(b) False

(c) True

(d) True

Example	Type of Reflex
(i) Sneezing	Simple
(ii) Blushing	Simple
(iii) Contraction of eye pupil	Simple
(iv) Lifting up a book	Conditioned
(v) Knitting without looking	Conditioned
(vi) Sudden application of brakes of the cycle on sighting an obstacle in front	Conditioned

(a) Association neuron: 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.

(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

(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

(a) CSF: Cerebrospinal fluid

(b) CNS: Central Nervous System

(c) PNS: Peripheral Nervous System

(d) ANS: Autonomic Nervous System

(a) Neuron: Neurons 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.

(a) Differences between cerebrum and cerebellum (function):

Cerebrum	Cerebellum
The cerebrum controls all voluntary actions. It enables us to think, reason, plan and memorize.	The cerebellum on the other hand maintains balance of the body and coordinates muscular activity.

(b) Differences between sympathetic nervous system and parasympathetic nervous system (location and role):

Sympathetic Nervous

System

Parasympathetic Nervous System

Sympathetic nervous system is located between the neck and the waist region.

Parasympathetic nervous system is located in the head and neck region and in sacral region.

It prepares the body for violent action against the abnormal condition.

It is concerned with re-establishing normal conditions after the violent act is over.

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

Sensory Nerve	Motor Nerve
Sensory nerve brings impulses from the receptors i.e. sense organs to the brain or spinal cord.	Motor nerve carries impulse from the brain or spinal cord to effector organs such as muscles or glands.

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

Cerebrum	Spinal Cord
The grey matter containing cytons lies in the cortex (outer region) while the white matter containing axons lies in the medullary region (inner region).	The grey matter containing cytons lies in the medullary region i.e. inner side while the white matter containing axons lies in the cortex i.e. the outer region.

(e) Differences between cranial nerves and spinal nerves (number in pairs):

Cranial Nerves	Spinal Nerves
There are 12 pairs of cranial nerves.	There are 31 pairs of spinal nerves.

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

Nerve impulse	Flow of electricity
Here, neither any substance nor any electrons or ions move along the nerve fibre.	Here, electrons actually move along the wire.
Nerve impulses travel at a speed of about 100 metres per second.	Electricity is conducted at a speed of about 150,000 km per second.

(g) Differences between medulla oblongata and cerebellum (function):

Medulla Oblongata	Cerebellum
Medulla oblongata controls the activities of internal organs and many other involuntary actions	The cerebellum maintains balance of the body and coordinates muscular activity.

Organ	Sympathetic System	Parasympathetic System
e.g. Lungs	Dilates bronchi and bronchioles	Constricts bronchi and bronchioles
1. Heart	Accelerates heartbeat	Retards heartbeat
2. Pupil of the eye	Dilates	Constricts
3. Salivary gland	Inhibits the secretion of saliva causing the drying of the mouth	Stimulates the release of saliva

(a) The brain and the spinal cord lie in the skull and the vertebral column respectively. 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.

The advantages of having a nervous system are as follows:

(a) Keeps us informed about the outside world through sense organs.

(b) Enables us to remember, think and reason out.

(c) Controls and harmonizes all voluntary muscular activities such as running, holding, writing

(d) Regulates involuntary activities such as breathing, beating of the heart without our thinking about them.

Myelinated Neuron

Reflex actions are involuntary actions which occur unknowingly. Voluntary actions on the other hand are performed consciously.

Picking up an apple and eating it is an example of voluntary action whereas withdrawal of hand on touching a hot object is an example of reflex action.

Reflex Action	Voluntary Action
Reflex actions are involuntary actions which occur unknowingly.	Voluntary actions on the other hand are performed consciously.
Commands originate in the spinal cord, autonomic nervous system and a few in the brain as well.	Commands originate in the brain.

Salivation is an example of conditioned reflex that develops due to experience or learning. Saliva starts pouring when you chew or eat food. Therefore, this reflex will occur not just on the sight or smell of food. The brain actually needs to remember the taste of food. Boy B started salivating because he must have tasted that food prior unlike boy A.

(a) 1 - Cerebrum, 2 - Cerebellum, 3 - Pons, 4 - Medulla oblongata.

(b) Meninges. The three layers of meninges are dura mater, arachnoid and pia mater.

(c) Neuron/nerve cell.

(d) Cerebellum (part 2) coordinates muscular activity and balance of the body.

Situation	Organ/body part	Change/action	Part of autonomic nervous system involved
1. You have entered a dark room	Eye	Pupil dilates	Sympathetic
2. Your body is consuming lot of glucose while running a race	Liver	Glycogen is converted into glucose in liver	Sympathetic
3. You are chewing a tasty food	Salivary gland	Salivation increases	Parasympathetic
4. You are running a race	Adrenal gland	Release of adrenaline and noradrenaline increases	Sympathetic
5. You are retiring to bed for sleep	Heart	Heart rate slows down	Parasympathetic
6. You are shivering in intense cold	Body hairs	Hair raised	Sympathetic

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

Class 10 SELINA Solutions Biology Chapter 10 - The Nervous System

The Nervous System Exercise Ex. 1

Solution A.1

Solution A.2

Solution A.3

Solution A.4

Solution A.5

Solution A.6

Solution A.7

Solution B.1

Solution B.2

Solution B.3

Solution C.1

Solution C.2

Solution C.3

Solution C.4

Solution C.5

Solution C.6

Solution C.7

Solution D.1

Solution D.2

Solution D.3

Solution D.4

Solution D.5

Solution D.6

Solution D.7

Solution E.1

Solution E.2

Solution E.3

Solution E.4

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