Samacheer Kalvi 10th Science Solutions Chapter 15 Pdf

Tamilnadu Board Samacheer Kalvi 10th Science Solutions Chapter 15: Tamilnadu State Board Solution Class 10 Science Chapter 15 – Nervous system.

Samacheer Kalvi 10th Science Solutions Chapter 15: Overview

Board	Samacheer Kalvi
Class	10
Subject	Science
Chapter	15
Chapter Name	Nervous system

Samacheer Kalvi 10th Science Solutions Chapter 15 Nervous system

I.) Choose the correct answer

1.) Bipolar neurons are found in

(a) retina of eye

(b) Cerebral cortex

(d) Respiratory epithelium

Ans:(a) retina of eye

Explanation: Because, bipolar neurons are found in the retina of eye and olfactory epithelium of nasal chamber.

2.) Site for processing of vision, hearing, memory, speech, intelligence and thought is

(a) kidney

(b) Ear

(d) Lungs

Ans: (c) Brain

Explanation: Because, the site processing of vision, hearing, memory, speech, intelligence and thought is only brain.

3.) In reflex action, the reflex arc is formed by

(a) Brain, spinal cord, muscle

(b) Receptor, muscle, spinal cord

(d) Receptor, spinal cord, muscle

Ans:(b) Receptor, muscle, spinal cord

Explanation: Because, receptor receives the touch or pain which is passed through sensory neurons i.e. muscles and reach to spinal cord.

4.) Dendrites transmit impulse—— cell body and axon transmit impulse —–cell body.

(a) Away from, away from

(b) Towards, away from

(d) away from, towards

Ans:(b) Towards, away from

Explanation: Because, dendrites transmit impulse away from the cell body and axon transmits impulse towards the cell body.

5.) The outer most of the three cranial meninges is

(a) Arachnoid membrane

(b) Piamater

(d) Myelin sheath

Ans:(c) Duramater

Explanation: Because, Dura matter is the outermost thick fibrous membrane.

6.) There are —-pairs of cranial nerves and—– pairs of spinal nerves.

(a) 12, 31

(b) 31, 12

(d) 12, 21

Ans: (a) 12, 31

Explanation: Because, there are 12 pairs of cranial nerves and 31 pairs of spinal nerves.

7.) The neurons which carries impulse from the central nervous system to the muscle fibre.

(a) Afferent neurons

(b) Association neuron

(d) Unipolar neuron

Ans:(c) Efferent neuron

Explanation: Because, the efferent neuron carries the impulse from the CNS to the muscle fibre.

8.) Which nervous band connects the two cerebral hemispheres of brain?

(a) Thalamus

(b) Hypothalamus

(d) Pons

Ans:(c) Corpus callosum

Explanation: Because, the two cerebral hemispheres are interconnected by thick band of nerve fibers called as corpus callosum.

9.) Node of Ranvier is found in

(a) Muscles

(b) Axons

(d) Cyton

Ans: (b) Axons

Explanation: Because, nodes of Ranvier is found in axons.

10.) Vomiting center is located in

(a) Medulla oblongata

(b) Stomach

(d) Hypothalamus

Ans:(a) Medulla oblongata

Explanation: Because, vomiting centre is located in medulla oblongata.

11.) Nerve cells do not possess

(a) Neurilemma

(b) Sarcolemma

(d) Dendrites

Ans:(b) Sarcolemma

Explanation: Because, nerve cells do not possesses sarcolemma.

12.) A person who met with an accident lost control of body temperature, water balance, and hunger. Which of the following part of brain is supposed to be damaged?

(a) Medulla oblongata

(b) Cerebrum

d) Hypothalamus

Ans: d) Hypothalamus

Explanation: Because, hypothalamus controls involuntary functions like hunger, thirst, sleep, sweating, sexual desire, anger, fear, water balance, blood pressure etc.

II.) Fill in the blanks

(1) —— is the longest cell in our body.

Ans:Axon is the longest cell in our body.

(2) Impulses travels rapidly in—— neurons.

Ans:Impulses travels rapidly in myelin sheath ofneurons.

(3) A change in the environment that causes an animal to react is called——-.

Ans:A change in the environment that causes an animal to react is called response.

(4) ——–Carries the impulse towards the cell body.

Ans:Dendrites carries the impulse towards the cell body.

(5) The two antagonistic component of autonomic nervous system——are——– and.

Ans:The two antagonistic component of autonomic nervous system are sympathetic and parasympathetic.

(6) A neuron contains all cell organelles except——-.

Ans:A neuron contains all cell organelles except Golgi apparatus in axon.

(7) ———maintains the constant pressure inside the cranium.

Ans:Cerebrospinal fluid maintains the constant pressure inside the cranium.

(8) ——-And——-increases the surface area of cerebrum.

Ans: Gyri andsulci increases the surface area of cerebrum.

The part of human brain which acts as relay center is——–.

Ans:The part of human brain which acts as relay center is thalamus.

III. State whether true or false, if false write the correct statement

(1) Dendrons are the longest fibres that conducts impulses away from the cell body.

Ans: False

Correct statement: Axons are the longest fibres which conducts impulses away from the cell body.

(2) Sympathetic nervous system is a part of central nervous system.

Ans: False

Correct statement: Sympathetic nervous system is a part of autonomic nervous system.

(3) Hypothalamus is the thermoregulatory centre of human body.

Ans: True

(4) Cerebrum controls the voluntary actions of our body.

Ans: True

(5) In the central nervous system myelinatedfibres form the white matter.

Ans: False

Correct statement: In the central nervous system, white or grey matter is formed with respect to the presence or absence of myelin sheath.

(6) All the nerves in the body are covered and protected by meninges.

Ans: False

Correct statement: The brain is covered by three connective tissue membrane or meninges.

(7) Cerebrospinal fluid provides nutrition to brain.

Ans: True

(8) Reflex arc allows the rapid response of the body to a stimulus.

Ans: True

(9) Pons helps in regulating respiration.

Ans: True

IV.) Match the following

Ans:

Nissil’s granules : Cyton
Hypothalamus : Forebrain
Cerebellum: Hindbrain
Schwann cell : Peripheral nervous system

V.) Understand the assertion statement. Justify the reason given and choose the correct choice

a.) Assertion is correct and reason is wrong

b.) Reason is correct and the assertion is wrong

c.) Both assertion and reason are correct

d.) Both assertion and reason are wrong

1.) Assertion: Cerebrospinal fluid is present throughout the central nervous system.

Reason: Cerebrospinal fluid has no such functions.

Ans:a. Assertion is correct and reason is wrong

2.) Assertion: Corpus callosum is present in space between the duramater and piamater.

Reason: It serves to maintain the constant intracranial pressure.

Ans:d. both assertion and reason are wrong

VI.) Short answer questions

1) Define stimulus.

Ans: The changes in the environmental conditions which are detected by receptors present in the body are called as the stimulus.

(2) Name the parts of the hind brain.

Ans: The hindbrain is formed of three parts that are cerebellum, pons and medulla oblongata.

(3) What are the structures involved in the protection of brain?

Ans: The brain is delicate vital structure which is protected in the bony cavity of skull. All the body activities are controlled by the centre which is brain. And it is connected by three connective tissue membranes or meninges which protects the brain.

1.) Dura matter is the outermost thick fibrous membrane.

2.) Arachnoid membrane is the middle, thin vascular membrane providing web like cushion.

3.) Piamater is the innermost, thin delicate membrane which is fully supplied with blood.

(4) Give an example for conditioned reflexes.

Ans: The conditioned reflexes are due to the results of learning and practicing. The best example of conditioned reflex is playing with harmonium, which needs more practice by which only, we can play harmonium by seeing on musical note pad. Mouth waters when we see the food we like is also an example of conditioned reflex.

(5) Which acts as a link between the nervous system and endocrine system?

Ans: Hypothalamus which acts as a thermoregulatory center of the body is an important link between nervous system and endocrine system.

It also helps in controlling hormones secreted by anterior pituitary gland.

(7) Define reflex arc.

Ans: The path or root taken by nerve impulse to complete reflex action is called as reflex arc.

VII.) Differentiate between

(1) Voluntary and involuntary actions.

Ans:

Voluntary actions:

The actions which are controlled by our own body and occurred according to our will are called as voluntary actions.
For example: eating
Voluntary actions are controlled by the brain and gives rise to muscular actions.

Involuntary actions:

The actions which are not controlled by our own body and not occurred according to our will are called as involuntary actions.
For example: breathing
Involuntary actions are mainly controlled by spinal cord and gives rise to muscular actions or sometime secretion of glands.

(2) Medullated and non-medullated nerve fibre.

Ans:

Medullated nerve fibre:

In this the nerve fibre is covered with the protective sheath named as mylein sheath which is again covered by a sheath called as neurilemma.
These nerves are white in colour and nodes of ranvier are present in them.
The nerves impulse carried out by medullated nerve fibre are faster than the non medullated nerve fibre.
Medullated nerve fibre are located in white matter of brain, spinal cord and also in the cranial and spinal nerves.

Non-medullated nerves fibre:

In this nerves fibre are covered with a single covering named as neurilemma.
This nerves are gray in colour and nodes of ranvier are absent in them.
The nerve impulses carried out by non-medullated nerves fibre are slower than the medullated nerve fibre.
Non-medullated nerves fibre are located in gray matter of brain, spinal cord and also in the autonomic nerves.

VIII.) Long answer questions

1) With a neat labelled diagram explain the structure of a neuron.

Ans:

The neurons or nerve cells are the structural and functional units of the nervous system. It is the longest cell in human body. It is mainly constructed of three parts namely cyton, dendrites and axons.

Cyton:

It is also named as body cell or perikaryon.
Cyton has centrally situated nucleus which abundant in cytoplasm called as neuroplasm.
The large body in the neuroplasm is called as Nissl’s granules and also other organelles such as ribosomes, lysosomes, mitochondria and endoplasmic reticulum are also present.
Neurons are unique in their nature because they do not have an ability to divide.
The neurofibrills present in the cytoplasm which helps in the transmission of nerve impulses.

Fig. structure of neuron

Dendrites:

Dendrites are projected from the cell body and helps in conducting the nerve impulses towards the cyton. The dendrites are in the form of branched projection and hence it increases the surface area for receiving the signals from other nerve cells.

Axon:

The axon is a single, elongated and slender projection. The ends of axions are having small branches which results into knob like swelling and hence called as synaptic knob.
The axon is having axolemma as a plasma membrane and axoplasm as a cytoplasm. Axon carries the impulses which are away from the cyton.
The axon is firstly covered with a protective sheath called as myelin sheath and which is also covered by a layer called as neurilemma.
The breaking of myelin sheath by depressions is called as nodes of ranvier.
Myelin sheath acts as insulator and thereby allows rapid transmission of nerve impulses.
The informal from one neuron to other will be passed through the synaptic junctions and releases the chemical from the synaptic knob called as neurotransmitter.

(2) Illustrate the structure and functions of brain.

The human brain is made up of three main parts namely The human brain is made up of three main parts namely forebrain, midbrain and hindbrain.

Fig. L. S. of Human brain

Forebrain:

The forebrain is made up of cerebrum and diencephalon.

Cerebrum:

• The two third portion of the brain forms the cerebrum. The cerebrum is longitudinally divided into left and right cerebral hemispheres and thses two cerebral hemispheres are connected internally through a thick layer of nerve cells called as corpus callosum.

• Externally each hemisphere is formed from gray matter called as cerebral cortex.

• The elevations formed due to folding of cortex externally is called as gyri and the depressions between them is called as sulci which increases the surface area.

• Each cerebral hemisphere is divided into four lobes which are also called as cerebral lobes and they are frontal lobe, parietal lobe, temporal lobe and occipital lobe.

• Thinking, intelligence, consciousness, memory, imagination, reasoning and willpower are the responsibilities of the cerebrum.

• Thalamus acts as the relay centre and it is the major conducting centre for sensory and motor signaling.

• Hypothalamus has function to control the involuntary actions like hunger, thirst, sleep, sweating, sexual desire, anger, fear, water balance and blood pressure. Also, it acts as a thermoregulatory center for the body.

Midbrain:

Midbrain is situated in between thalamus and hindbrain. The dorsal portion of midbrain has four rounded bodies called as corpora quadrigemina which controls visual and auditory reflexes.

Hindbrain:

Hindbrain is made up of three parts namely cerebellum, pons and medulla oblongata.
Cerebellum:
Cerebellum is the second largest part of the brain which is made up of two large sized hemispheres and middle vermis. The voluntary movements are coordinated by cerebellum and it also maintains body balance.

Pons:

• It is the bridge for nerve fibre and connects the lobes of cerebellum. The signals between cerebellum, spinal cord, midbrain and cerebrum are relayed by the pons.

• It also controls the respiration and sleep cycle.

• Medulla oblongata: It connects spinal cord and various parts of brain and it is the posterior most part of the brain.

• It consists of cardiac centres, respiratory centres, and vasomotor centres to control heartbeat, respiration and contraction of blood vessels respectively. Vomiting and salivation is regulated by medulla oblongata.

The functions of some part of the brain are as given below.

• Cerebral cortex helps in sensory perception, control of voluntary functions, language, thinking, decision making and creativity.

• Thalamus acts as the relay centre.

• Hypothalamus is the link between nervous system and endocrine glands and it controls the temperature, thirst, hunger and urination.

• Cerebellum maintains the posture and balance and coordinate voluntary muscle activity.

• Pons and medulla plays a role in sleep-awake cycle and acts as centre for cardiovascular, digestive and respiratory control.

(3) What will you do if someone pricks your hand with a needle? Elucidate the pathway of response with a neat labelled diagram.

Ans:

Fig. Reflex action and its pathway

When our hand is pricked by a needle then the prick pain is the touch which is sensed by the sense organ skin acting as a receptor.
This stimulus thereafter creates an impulse in the sensory neuron and sensory neuron transmits it to the spinal cord.
Then spinal cord detects the stimulus and impulse is passed towards the relay neuron and finally transmitted to a motor neuron.
Motor neuron takes command from spinal cord CNS and gives to our hand due to which the muscles of our hand get immediately contracted and we will withdraw our hand.
In this way reflex action is formed when our hand is pricked by a needle.

(4) Describe the structure of spinal cord.

Ans:

Spinal cord is the cylindrical structure located in the neural canal of the vertebral column. It is covered with meninges and extended from lower end of medulla oblongata to the first lumbar vertebra.
The spinal cord contains cerebrospinal fluid which is filled with cavity called as central canal. The gray matter in the spinal cord is H- shaped, where upper ends shows posterior horns and lower ends shows anterior horns.
The dorsal or afferent root is formed by passing bundles of fibre through posterior horns while ventral or efferent root is formed by passing bundles of fibre through the anterior horns.
These two roots joins and forms the spinal nerves. Externally white matter is present having bundles of nerve tracts.
The sensory and motor impulses to and from the brain are conducted by spinal cord. Also it controls the reflex action of the body.

(5) How nerve impulses are transferred from one neuron to next neuron?

Ans:

The sense organs such as eyes, the nose, and the skin are the receptors which detects all the information from the environment.
Receptors transmits information in the form of electrical impulse and it is received by the dendritic tips of the neuron.
The impulse from dendrites to cell body is transmitted and then along the axon up to its end. After reaching the axonal end it forces the nerve endings to release the chemical neurotransmitter which diffuse with the synapse and starts same electrical impulse in the dendrites of the next neuron and in this way their cell body is carried along the axon.
And finally the electrical impulse reaches the brain or spinal cord and the response from the brain is passed to the effector organs like muscle or gland cells which undergoes different response, in the same way.
The flow of nerve impulse from the axonal end of one neuron to the dendrites of the other neuron through the synapse is called as synaptic transmission.
In this way, nerve impulses are transferred from one neuron to next neuron.

(6) Classify neurons based on its structure.

Ans:

Neurons are of different types on the basis of their structure and functions which are explained as follows.
Firstly, on the basis of structure neurons are classified as below:

(1) Unipolar neurons:

In unipolar neurons, only one nerve is arises from cyton and it acts as both axon and Dendron.

(2) Bipolar neurons:

In bipolar neurons, the cyton gives rise to two neurons out of which one acts as axon and another acts as a Dendron.

(3) Multiple neurons:

In multiple neurons, the cyton gives rise to many axons and Dendron.

IX.) Higher Order Thinking Skills (HOTS)

(1) ‘A’ is a cylindrical structure that begins from the lower end of medulla and extend downwards. It is enclosed in bony cage ‘B’ and covered by membranes ‘C’. As many as ‘D’ pairs of nerves arise from the structure ‘A’.

Ans:

(i) What is A?

A is the spinal cord.

(ii) Name (a) bony cage ‘B’ and (b) membranes ‘C’

Bony cage B is the vertebral column

Membranes C is meninges

(iii) How much is D?

D is the 31 pairs of spinal nerves.

Because, spinal cord is the cylindrical structure which lie in the neural canal of the vertebral column and which extends from lower end of medulla oblongata to the first lumbar vertebra. It is also covered by meninges.And there are 31 pairs of spinal nerves.

(2) Our body contains a large number of cells ‘L’ which are the longest cells in the body. L has long and short branch called as ‘M’ and ‘N’ respectively. There is a gap ‘O’ between two ‘L’ cells, through which nerve impulse transfer by release of chemical substance ‘P’.

Ans:

(i) Name the cells L

L is the cell called as neuron.

(ii) What are M and N?

M is the Axon and N is the Dendron.

(iii) What is the gap O?

Gap O is the synaptic knob.

(iv) Name the chemical substance P

P is the chemical called as neurotransmitter.

Because, neuron is the longest cell of the human body having long and short branch called as Axons and Dendron.

And junction between synaptic knob of axon of one neuron and Dendron of next neuron is called synaptic junction through which nerve impulse is transferred by releasing the chemical substance called as neurotransmitters.