NCERT Solutions Class 10 Science Chapter 7 || Control and coordination additional questions solution || Class 10 Chapter 7 Additional questions solution || Biology || Science ||

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                                 Page: 119

Ques 1: What is the difference between a reflex action and walking? 

Ans 1: » A reflex action is an automatic, rapid response to a stimulus. It does not involve any thinking. For example, we close our eyes immediately when the bright light is focused on our eyes. 

» Walking, on the other hand, is a voluntary action. It is u under our conscious control. 

Ques 2: What happens at the synapse between two neurons? 

Ans 2: A very small gap that occurs b/w the last portion of the axon of one neuron and the dendrite of other neuron is known as a synapse. It acts as an one way valve to transmit impulses in one direction only.

This one-directional transfer of impulses occurs as the chemicals are produced on only one side of the neuron i.e., the axon’s side. From axon, the impulses t travels across the synapse to the dendrite of the other neuron.

Ques 3: Which part of the brain maintains posture and equilibrium of the body? 

Ans 3: Cerebellum, a part of hindbrain is responsible for maintaining the posture and  equilibrium of the body. 

Ques 4: How do we detect the smell of an agarbatti (incense stick)? 

Ans 4: The thinking part of our brain is the forebrain. It is having a separate areas that are  specialized for hearing, smelling, sight, taste, touch, etc. The forebrain also has regions that collects 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 the other receptors and also with the information already stored in the brain. 

Ques 5: What is the role of the brain in reflex action? 

Ans 5: Reflex actions are the 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 takes time which would be enough to get us 🔥burnt. The sensory nerves that detect the heat are connected to the nerves that moves 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 are present between the input and output nerves − meet in a bundle in the spinal cord.


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.

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Ques 1: What are plant hormones?

Ans 1: Plant hormones (phytohormones) are naturally-occurring organic substances. These are synthesized in only one part of the plant body (in minute quantities) and are translocated to the other parts when required. The five major types of phytohormones are gibberellins, auxins, , cytokinins, abscisic acid and ethylene.

» Gibberellins help in the growth of the stem.

» Auxins help in the growth of the stem. 

» Cytokinins promote the cell division.

» Abscisic acid is one example of a hormone which inhibits growth. 

Ques 2: How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Ans 2:  » The movement of the leaves of sensitive plant, Mimosa pudica or “touch me not”, plant occurs in response to touch or contact stimuli. This is done by plant cells by changing the amount of water balance in the leaves. This movement is independent of growth. 

» The movement of the shoot towards the light is known as phototropism. This type of movement is directional and is growth dependent.

Ques 3: Give an example of a plant hormone that promotes growth.

Ans 3: Examples of plants growth promoters hormones:

» Gibberellins help in the growth of the stem.

» Auxins help in the growth of the stem. 

» Cytokinins promotes cell division.

Ques 4: How do auxins promote the growth of a tendril around a support? 

Ans 4: These tendrils s are sensitive to touch. When they come in contact with any support, auxin (a growth promoter hormone) diffuses from the p part of the tendril in contact with the object to other side, which is not in the contact. Therefore the part of the tendril in the contact with the object does not grow as rapidly as the part of the tendril far from the object. This causes the tendril to circle around the object and thus climb to it. 

Ques 5: Design an experiment to demonstrate hydrotropism. 

Ans 5: Take 2 small beakers and label them as C and D. Fill beaker C with water. Now make a cylindrical-shaped roll from a filter paper and keep it as a bridge between beaker C and beaker D, as shown in the figure below. Attach a few germinating seeds in the middle of the filter paper bridge. Now, cover the e entire set-up with a transparent plastic container so that the moisture is retained.


Observation: 

The roots of the germinating seeds will grow towards the beaker C. This experiment demonstrates the phenomenon of hydrotropism
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Ques 1: How does chemical coordination take place in animals? 

Ans 1: Chemical coordination takes place in the animals with the help of hormones. Hormones are the chemical messenger that regulates the physiological processes in living organisms. It is secreted by glands. The regulation of the 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 physiological processes of the body. 

Ques 2: Why is the use of iodised salt advisable? 

Ans 2: Iodine stimulates the thyroid gland to produce hormone known as thyroxin hormone. It regulates carbohydrate, fat, and protein metabolism in our body. Deficiency of this hormone results in the enlargement of the thyroid gland (present near the neck). This can lead to goitre, a disease characterized by swollen neck. Therefore, iodised salt is advised for  normal functioning of the thyroid gland. 

Ques 3: How does our body respond when adrenaline is secreted into the blood? 

Ans 3: Adrenalin is a hormone which is secreted by the adrenal glands in case of any danger or emergency or any other kinds of stress. It is secreted directly into the blood and is transported to other parts of the body. 

When secretion is 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 the rib muscles. It also increases the BP(blood pressure) . All these  responses enables the body to deal with any stress or emergency.

Ques 4: Why are some patients of diabetes treated by giving injections of insulin? 

Ans 4: Diabetes is a disease in which the level of sugar in the blood is too high. Insulin, Insulin is a hormone secreted by the pancreas, helps in regulating the blood sugar levels. That’s the reason why diabetic patients are treated by giving injections of insulin.

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