Chapter 23: Control and Coordination

NIOS Class 10 Science Chapter 23 Question Answers

INTEXT QUESTIONS 23.1

1. Can you think of a real-life example when teamwork helped you to achieve something that you could not have done by yourself? Please write about this incident in 3-5 sentences.

Ans: There is no single correct answer. There may be diverse examples. For instance, in farming, a group of people till the land, another group sows the seeds, someone else takes care of the crops, and only then does everyone enjoy the bounty of a good harvest.

2. Give one example of coordination of a process taking place in our body, which is brought about by both the nervous system and hormonal system.

Ans: Secretion of digestive juices

INTEXT QUESTIONS 23.2

1. The structural and functional unit of the nervous system is (encircle the correct alternative out of the following)

(a) Nephron

(b) Neuron

(d) Axon

Ans: (b) Neuron

2. Consider that you are passing by a garbage disposal area and you immediately cover your nose. Arrange the events below in a logical order by marking them from 1 to 5 to trace the events that happen in the nervous system from the detection of foul smell (stimulus generation) to covering your nose (response).

(i) At the end of the axon, the electrical impulse releases chemicals

(ii) Stimulus received on the dendritic cells of a neuron sets off a chemical reaction that creates an electrical impulse

(iii) Electrical impulse transmitted through the cell body and axon

(iv) The chemicals cross the synapse and reach the next neuron. Similarly, the electrical impulse crosses several neurons

(v) Finally, the impulse is delivered from the neuron to the gland that helps in recognition of the foul smell and muscle cells that help in covering the nose

Ans: The sequence should be: ii, iii, i, iv, v

3. With the help of a suitable example, explain the term ‘stimulus.’

Ans: A stimulus is an agent or an environmental change that can initiate a response in the body. The stimuli can be of several types. It could be physical (touch, prick, pressure), auditory, chemical, radiant (light), heat or cold, or electrical.

INTEXT QUESTIONS 23.3

Fill in the blanks:

(i) The central nervous system consists of ________ and _____________.

(ii) The two functions of the cerebrum are _________ and ____________.

(iii) The major function of the cerebellum is to maintain ________ of the body.

(iv) The ________________ part of the brain controls the activity of all internal organs of our body.

(v) The outer and inner regions of the cerebrum are composed of _______ and __________ matter respectively.

Ans:

(i) Brain and spinal cord

(ii) Intelligence and consciousness

(iii) Balance

(iv) Medulla/ medulla oblongata

(v) Gray matter, white matter

INTEXT QUESTIONS 23.4

1. Name the two types of reflexes.

Ans: Natural reflex and conditioned reflex.

2. Given below are the different components of a reflex arc in a haphazard manner. Arrange them in the correct order in the space provided below:

Sensory neuron, Effector, Stimulus, CNS, Receptor, Response, Motor neuron

Ans: Stimulus —> receptor —> sensory neuron —> CNS—> motor neuron —> effector —> response.

3. Now that you are aware of the well-thought-out voluntary actions that are coordinated by the cerebrum and immediate response actions or reflex actions, coordinated by the spinal cord, try to identify whether the following situations may be best managed by well-thought-out voluntary actions or quick response reflex actions. Please provide at least one reason for your choice.

Situation	Appropriate action voluntary action or reflex)	Reason for your choice
You need to immediately stop your bicycle as a speeding motorbike comes in front of your bicycle.
You have scored good marks in all the subjects in class X and now need to choose between the science and commerce streams. Your family feels you should study science, while you like numbers and would like to study commerce.
You are cleaning your cupboard, a sharp needle pokes you, and you remove your hand immediately.
You have moved to a new neighborhood and are trying to make new friends.

Ans: Correct response has been provided in italics for the column on ‘Appropriate Action.’ However, there is no single correct reason for the choice that the learner makes. The evaluator needs to keep in mind that the learner is providing logical reasons for their choice.

Situation	Appropriate action voluntary action or reflex)	Reason for your choice
You need to immediately stop your bicycle as a speeding motorbike comes in front of your bicycle.	Reflex Action	It is an emergency, and there is no time to process information through the central nervous system.
You have scored good marks in all the subjects in class X and now need to choose between the science and commerce streams. Your family feels you should study science, while you like numbers and would like to study commerce.	Well thought-out voluntary action	It is an emergency, and there is no time to process information through the central nervous system.
You are cleaning your cupboard, a sharp needle pokes you, and you remove your hand immediately.	Reflex Action	It is an emergency, and there is no time to process information through the central nervous system.
You have moved to a new neighborhood and are trying to make new friends.	Well thought-out voluntary action	It is important to choose friends who care for you and wish you well. Hence, it has to be a well-thought-out action.

INTEXT QUESTIONS 23.5

1. How many pairs of cranial nerves are present in our body?

Ans: 12 pairs

2. Name the two parts of the autonomic nervous system.

Ans: Sympathetic and parasympathetic

INTEXT QUESTIONS 23.6

1. Fill in the blanks:

(i) A hormone is transported by the …………………. to the target organ.

(ii) Hypoactivity of the thyroid gland causes …………….. leading to cretinism in young children.

(iii) The pancreas secretes two hormones, which help in the …………. of glucose in our body.

Ans:

Blood
Goitre
Metabolism

2. Each of the following statements has one correct response. Please choose the correct option and encircle it.

(i) If a pathologist were to collect a hormone, where would it be collected from?

(a) Blood

(b) Brain

(d) Any part of the body

Ans: (a) Blood

(ii) Hyperactivity of the pituitary gland causes:

(a) Dwarfism

(b) Gigantism

(d) Cretinism.

Ans: (c) Cushing’s disease

(iii) The neurons that carry impulses from sense organs to the brain or spinal cord are:

(a) Sensory neuron

(b) Motor neuron

(d) Connecting neuron

Ans: (a) Sensory neuron

(iv) The parts of a reflex are connected to:

(a) Brain

(b) Spinal cord

(d) A synapse

Ans: (c) Both brain and spinal cord

(v) Two neurons are connected to each other through:

(a) Their axons

(b) Their dendrons

(d) Synapse

Ans: (d) Synapse

(vi) An axon is:

(a) A nerve fibre

(b) A bundle of dendrites

(d) The sheath of a nerve fibre.

Ans: (d) The sheath of a nerve fibre.

(vii) An individual reported to the neurophysician with a body temperature much higher than normal. After several investigations, the neurophysician diagnosed that a tumor in a specific area of the brain was causing this symptom. Where do you think the tumor may have been located?

(a) Cerebrum

(b) Cerebellum

(d) Diencephalon

Ans: (c) Hypothalamus

(viii) Where is the subconscious mind located?

(a) Thalamus

(b) Hypothalamus

(d) Cerebrum

Ans: (d) Cerebrum

(ix) Hyposecretion of insulin causes:

(a) Diabetes

(b) Goitre

(d) Gigantism

Ans: (a) Diabetes

(x) Which part of our brain helps in maintaining the balance of our body?

(a) Cerebrum

(b) Cerebellum

(d) Hypothalamus

Ans: (b) Cerebellum

(xi) Sudha likes to sleep in, and someone always has to wake her up in the morning. However, during exams, she is able to get up without an alarm or any other help. Which part of the nervous system helps her to deal with this situation?

Sleep in sleeping beyond waking hours

(a) Parasympathetic nervous system

(b) Medulla

(d) Cerebrum

Ans: (c) Sympathetic nervous system

TERMINAL EXERCISES

A. Tick the correct answer of the following

1. The three protective coverings over the brain also called:

(A) Membranes

(B) Layers

(D) Sheaths

Ans: (C) Meninges

2. Which part of the brain controls the body temperature?

(A) Cerebrum

(B) Cerebellum

(D) Medulla oblongata

Ans: (C) Hypothalamus

3. The spinal cord is extended from the medulla up to the whole length of the vertebral column and lies within the:

(A) Neural canal

(B) Vertebral canal

(D) Eustachian canal

Ans: (B) Vertebral canal

4. Which one of the following hormones is secreted by the pancreas?

(A) Prolactin

(B) Thyroxin

(D) Insulin

Ans: (D) Insulin

B. Answer briefly:

1. What is the nature of the membranes covering the brain? What is the name of the fluid that fills the space between these membranes? What is its role?

Ans:

(i) Dura mater, the outermost tough fibrous membrane
(ii) Arachnoid, the thin, delicate middle layer giving a web-like cushion
(iii) Pia mater, the innermost highly vascular membrane, richly supplied with blood.

The space between the covering membranes is filled with a watery fluid known as cerebrospinal fluid, which acts like a cushion to protect the brain from shocks.

2. Describe the three regions of the brain.

Ans: The brain consists of three important parts: Cerebrum, Cerebellum, and Medulla.

(a) Cerebrum: It is the largest portion of the brain, vertically divided into two halves: right and left cerebral hemispheres. Their outer surface is highly convoluted with ridges and grooves.
(b) The cerebellum is a much smaller area of the brain located below the cerebrum. It has no convolutions, but has numerous furrows. This also has an outer cortex made up of gray matter and an inner white matter.
(c) The medulla oblongata is the lowest portion of the brain located at the base of the skull. It is roughly triangular and is continued behind as the spinal cord.

3. Differentiate between the following pairs of terms:

(i) Sensory nerve and motor nerve

(ii) Cerebrum and cerebellum.

(iii) Sympathetic and parasympathetic nervous system

Ans:

(i) Sensory nerve and motor nerve:

Sensory nerves that contain sensory fibres. These nerves bring impulses from the receptors (sense organs) to the brain or spinal cord. Example: Optic nerve arising from the eye and ending in the brain.
Motor nerves, which contain motor fibres. These nerves carry impulses from the brain or spinal cord to the effector organs, like muscles or glands. Example: a nerve arising from the brain and carrying an impulse to the muscles of the eye.

(ii) Cerebrum and cerebellum:

Cerebrum: It is the largest portion of the brain, vertically divided into two halves: right and left cerebral hemispheres. Their outer surface is highly convoluted with ridges and grooves.
The cerebellum is a much smaller area of the brain located below the cerebrum. It has no convolutions, but has numerous furrows. This also has an outer cortex made up of gray matter and an inner white matter.

(iii) Sympathetic and parasympathetic nervous system:

The Sympathetic Nervous System (SNS) becomes more active during times of stress. It prepares the body for action. Its action during the stress response comprise the ‘fight-or-flight response’ that is manifested largely under the influence of the hormone, adrenaline.
The Parasympathetic Nervous System executes actions that do not require immediate response, for example, the production of saliva and tears, digestion, etc.

4. Define the following terms:

(i) Receptor

(ii) Synapse

(iii) Hormone

(iv) Neuron

(v) Impulse

(vi) Stimulus

(vii) Effector

Ans:

(i) Receptor: Receptors are sensory organs, such as the nose, eyes, ears, etc., that pass impulses to the sensory nerves.
(ii) Synapse: It is the junction between two neurons.
(iii) Hormone: Hormones are chemicals that are produced by specialized glands and are secreted directly into the blood.
(iv) Neuron: Individual cells of the nervous system are called neurons.
(v) Impulse: Impulse is the electrical signal passed from one neuron to the next one.
(vi) Stimulus: A stimulus is an agent or an environmental change that can initiate a response in the body.
(vii) Effector: It is the muscle or other body part that responds to the impulse.

5. Given below is a table regarding various hormones secreted by the pituitary gland, and functions of these secretions. Fill in the blanks (1 to 4);

Hormones secreted	Functions
Somatotropic hormone	______________(1)____________
__________(2)____________	Helps in the metabolism of glucose in our body
Thyroid hormone	____________(3)__________
__________(4)_____________	In males, it stimulates the secretion of testosterone.

Ans:

Hormones secreted	Functions
Somatotropic hormone	(1) Growth Hormone
(2) Insulin	Helps in the metabolism of glucose in our body
Thyroid hormone	(3) Regulate metabolism in the body
(4) Gonad Stimulating Hormone	In males, it stimulates the secretion of testosterone.

6. Imagine that you did not score good marks in your science exam. Do you:

(a) Tear the mark sheet and not let your parents know about it?

(b) Decide that you are not a good student and cannot study science any further?

(c) Discuss your mistakes with the teacher and ask for help from the teacher or another student who has done well and is willing to help you?

Please choose one of the three options above and provide two reasons for your choice

Ans: Write your own answer.

7. Imagine that you have gone out with three friends. One of them starts smoking and offers the cigarette to the rest of you. One of your friends accepts the offer hesitatingly and also encourages you to try smoking. One amongst you refuses to smoke and says that he did not know that he was in bad company. This person leaves the group in a huff. You also do not want to smoke, but at the same time, you have been friends with this group for many years now and would like to continue your friendship.

Please describe in 2-4 sentences how you will communicate with your friends in an attempt to save your friendship without accepting their offer to smoke.

Please note: There is no single correct answer. The learner needs to demonstrate use of assertive communication skills.

Ans: Write your own answer.

8. After a week, you go out again with the two friends who had asked you to try smoking a cigarette. This time, they tell you that it is smart or stylish to smoke and in order to be part of the group, you should also smoke. Would you like to continue/ not continue being friends with them?

Please state your decision and provide at least two reasons for your decision.

Please note: There is no single correct answer. The purpose of this activity is to enable the learner to appreciate that friends never pressurize to do things that someone is uncomfortable with. The learner also needs to realise that exploitative relationships, including friendships, should be terminated.

Ans: Write your own answer.

9. When a barefoot person accidentally steps on a pin, what will be her/ his immediate response? Explain how this reaction is processed by the nervous system.

Ans: The immediate action will be to remove the foot instantly when it comes in contact with the pin. This is due to reflex action controlled by the spinal cord without the involvement of the brain. Reflex actions are involuntary and spontaneous. It flows from,

Stimulus → receptor in the sense organ → afferent (sensory) nerve fibre → CNS → efferent (motor) nerve fibre → muscle (to contract)/gland (to secrete)

10. Give one function performed by each of the following:

1. Cerebrum

2. Cerebellum.

3. Hypothalamus

4. Medulla oblongata

5. Cerebrospinal fluid

Ans:

1. Cerebrum: Cerebrum helps us to make well-thought-out and informed decisions.
2. Cerebellum: Helps us walk by coordinating different muscles.
3. Hypothalamus: Controls body temperature
4. Medulla oblongata: Its function is to control the activities of our visceral organs, like the alimentary canal, movement, breathing, beating of the heart, and many other involuntary actions.
5. Cerebrospinal fluid: It acts as a shockproof cushion and forms a medium for the exchange of food materials, waste products, and respiratory gases with neurons.