NCERT Class 10: Science-Intext Solutions

Chapter 07-Control and Coordination-Intext Solutions

NCERT Book Page Number-119
Q.1. What is the difference between a reflex action and walking?
Ans. A reflex action is a rapid automatic response to a stimulus. It does not involve any thinking process. For example, we close our eyes immediately when the bright light is focused. Walking, on the other hand, is a voluntary action. It is under our conscious control.
Q.2. What happens at the synapse between two neurons?
Ans. A very small gap that occurs between the endings of axon of one neuron and the dendrites of the other neuron is known as a synapse. It acts as a one way valve to transmit impulses in one direction only. This unit-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 dendrites of the other neuron.


Q.3. Which part of the brain maintains posture and equilibrium of the body?
Ans. Cerebellum, a part of hindbrain is responsible for maintaining posture and equilibrium of the body.
Q.4. How do we detect the smell of an agarbatti (incense stick)?
Ans. The thinking part of our brain is the forebrain. It has separate areas that are specialised 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 by putting it together with the information received from other receptors and also with the information already stored in the brain.
Q.5. What is the role of the brain in reflex action?
Ans. 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.
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 Book Page Number-122

Q.1. What are plant hormones?
Ans. Plant hormones or phytohormones are naturally occurring organic substances. These are synthesised in one part of the plant body (in minute quantities) and are translocated to otherparts when required. The five major types of phytohormones are auxins, gibberellins, cytokinins, abscisic acid and ethylene.
Q.2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?
Ans. 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 growth dependent.
Q.3. Give an example of a plant hormone that promotes growth.
Ans. Auxin is an example of growth – promoting plant hormone.
Q.4. How do auxins promote the growth of a tendril around a support?
Ans. Auxin is synthesised 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.
Q.5. Design an experiment to demonstrate hydrotropism.
Ans. 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 Book Page Number-125
Q.1. How does chemical coordination take place in animals?
Ans. 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 come under the endocrine system. The nervous system along with the endocrine system in our body controls and coordinates the physiological processes.
Q.2. Why is the use of iodised salt advisable?
Ans. Iodine stimulates the thyroid gland to produce thyroxin hormone which 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 characterised by swollen neck. Therefore, iodised salt is advised for normal functioning of thyroid gland.
Q.3. How does our body respond when adrenaline is secreted into the blood?
Ans. Adrenalin is a hormone secreted by the adrenal glands in case of any danger or emergency or any kind 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.
Q.4. Why are some patients of diabetes treated by giving injections of insulin?
Ans. Diabetes is a disease in which the level of sugar in the blood is too high. Insulin, a hormone secreted by the pancreas, helps in regulating the blood sugar levels. This is the reason why diabetic patients are treated by giving injections of insulin.