CBSE Class X

NCERT Solution Class X Science Control and Coordination Question 5 (Ex 7.4)

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Question 5:

Draw the structure of a neuron and explain its function.

Answer:

Neurons are the functional units of the nervous system. The three main parts of a

neuron are axon, dendrite, and cell body.

Structure of a neuron
Functions of the three parts of a neuron:

Axon: It conducts messages away from the cell body.

Dendrite: It receives information from axon of another cell and conducts the

messages towards the cell body.

 

Cell body: It contains nucleus, mitochondria, and other organelles. It is mainly

concerned with the maintenance and growth.

NCERT Solution Class X Science Control and Coordination Question 4 (Ex 7.4)

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Question 4:

What is the function of receptors in our body? Think of situations where receptors do

not work properly. What problems are likely to arise?

Answer:

Receptors are sensory structures (organs/tissues or cells) present all over the body.

The receptors are either grouped in case of eye or ear, or scattered in case of skin.

Functions of receptors:

(i) They sense the external stimuli such as heat or pain.

(ii) They also trigger an impulse in the sensory neuron which sends message to the

     spinal cord.When the receptors are damaged, the external stimuli transferring

     signals to the brain are not felt. For example, in the case of damaged receptors,

     if we accidentally touch any hot object, then our hands might get burnt as

     damaged receptors cannot perceive the external stimuli of heat and pain.

NCERT Solution Class X Science Control and Coordination Question 3 (Ex 7.3)

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Question 3:

How does our body respond when adrenaline is secreted into the blood?

Answer:

Adrenalin is a hormone secreted by the adrenal glands in case of any danger or

emergency or any kinds of stress. It is secreted directly into the blood and is

transported to different parts of the body.

When secreted in large amounts, it speeds up the heartbeat and hence supplies more

oxygen to the muscles. The breathing rate also increases due to contractions of

diaphragm and rib muscles. It also increases the blood pressure. All these responses

enable the body to deal with any stress or emergency.

NCERT Solution Class X Science Control and Coordination Question 2 (Ex 7.3)

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Question 2:

Why is the use of iodised salt advisable?

Answer:

Iodine stimulates the thyroid gland to produce thyroxin hormone. It regulates

carbohydrate, fat, and protein metabolism in our body. Deficiency of this hormone

results in the enlargement of the thyroid gland. This can lead to goitre, a disease

characterized by swollen neck. Therefore, iodised salt is advised for normal

functioning of the thyroid gland.

NCERT Solution Class X Science Control and Coordination Question 1 (Ex 7.3)

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Question 1:

How does chemical coordination take place in animals?

Answer:

Chemical coordination takes place in animals with the help of hormones.Hormone is

the chemical messenger that regulates the physiological processes in living organisms.

It is secreted by glands. The regulation of physiological processes, and control and

coordination by hormones comes under the endocrine system. The nervous system

along with the endocrine system in our body controls and coordinates the physio-

logical processes.

NCERT Solution Class X Science Control and Coordination Question 5 (Ex 7.2)

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Question 5:

Design an experiment to demonstrate hydrotropism.

Answer:

Take two small beakers and label them as A and B. Fill beaker A with water. Now

make a cylindrical-shaped roll from a filter paper and keep it as a bridge between

beaker A and beaker B, as shown in the figure. Attach few germinating seeds in the

middle of the filter paper bridge. Now, cover the entire set-up with a transparent

plastic container so that the moisture is retained.

 

Observation:

The roots of the germinating seeds will grow towards beaker A.

This experiment demonstrates the phenomenon of hydrotropism.

NCERT Solution Class X Science Control and Coordination Question 4 (Ex 7.2)

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Question 4:

How do auxins promote the growth of a tendril around a support?

Answer:

Auxin is synthesized at the shoot tip. It helps the cell grow longer. When a tendril

comes in contact with a support, auxin stimulates faster growth of the cells on the

opposite side, so that the tendril forms a coil around the support. This makes the

tendrils appear as a watch spring.

NCERT Solution Class X Science Control and Coordination Question 2 (Ex 7.2)

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Question 2:

How is the movement of leaves of the sensitive plant different from the movement

of a shoot towards light?

Answer:

The movement of leaves of the sensitive plant, Mimosa pudica or “touch me not”,

occurs in response to touch or contact stimuli. This movement is independent of

growth. The movement of shoot towards light is known as phototropism. This type

of movement is directional and is growth dependent.

NCERT Solution Class X Science Control and Coordination Question 1 (Ex 7.2)

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Question 1:

What are plant hormones?

Answer:

Plant hormones or phytohormones arenaturally-occurring organic substances. These

are synthesized in one part of the plant body (in minute quantities) and are

translocated to other parts when required. The five major types of phytohormones

are auxins, gibberellins, cytokinins, abscisic acid, and ethylene.

NCERT Solution Class X Science Control and Coordination Question 5 (Ex 7.1)

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Question 5:

What is the role of the brain in reflex action?

Answer:

Reflex actions are sudden responses, which do not involve any thinking. For example,

when we touch a hot object, we withdraw our hand immediately without thinking as

thinking may take time which would be enough to get us burnt.

The sensory nerves that detect the heat are connected to the nerves that move the

muscles of the hand. Such a connection of detecting the signal from the nerves

(input) and responding to it quickly (output) is called a reflex arc. The reflex arcs

−connections present between the input and output nerves − meet in a bundle in

the spinal cord.

 

Reflex arc

Reflex arcs are formed in the spinal cord and the information (input) reaches the

brain. The brain is only aware of the signal and the response that has taken place.

However, the brain has no role to play in the creation of the response.

NCERT Solution Class X Science Control and Coordination Question 4 (Ex 7.1)

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Question 4:

How do we detect the smell of an agarbatti (incense stick)?

Answer:

The thinking part of our brain is the forebrain. It has separate areas that are

specialized for hearing, smelling, sight, taste, touch, etc. The forebrain also has

regions that collect information or impulses from the various receptors. When the

smell of an incense stick reaches us, our forebrain detects it. Then, the forebrain

interprets it by putting it together with the information received from other receptors

and also with the information already stored in the brain.

NCERT Solution Class X Science Control and Coordination Question 2 (Ex 7.1)

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Question 2:

What happens at the synapse between two neurons?

Answer:

A very small gap that occurs between the last portion of axon of one neuron and the

dendron of the other neuron is known as a synapse. It acts as a one way valve to

transmit impulses in one direction only. This uni-direction transfer of impulses occurs

as the chemicals are produced in only one side of the neuron i.e., the axon’s side.

From axon, the impulses travel across the synapse to the dendron of the other

neuron.

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