Lesson: Control and Coordination  

Question 1

What is the difference between a reflex action and walking?


A reflex action is an unconscious involuntary action. It is a rapid and automatic response to an external stimulus. On the other hand, walking is a voluntary action. It is under our control.

Question 2

What happens at the synapse between two neurons?


A synapse is the gap between two neurons. At the synapse, electrical signals are converted into chemicals. These chemicals can easily cross the gap and pass on to the next neuron. Here it is again converted into electrical signals. The impulses or signals are transmitted in one direction only.

Question 3

Which part of the brain maintains posture and equilibrium of the body?


Cerebellum which is a part of hind brain is responsible for maintaining posture and equilibrium of a body.

Question 4

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


When the smell of an incense stick reaches our nose, the olfactory receptors present in our nose detect it. These receptors send information to the fore-brain in the form of electrical signals. The fore-brain interprets this information, from stored memory, as the smell of an incense stick.

Question 5

What is the role of brain in reflex action?


A brain has no direct involvement in reflex action. Reflex actions are very quick. They do not require thinking. They are mainly controlled by the spinal cord.

Question 6

What are plant hormones?


Plant hormones:

(a) Are known as phytohormones.

(b) Are chemical substances that are secreted within a plant

(c) Regulate the growth and development of a plant.

There are five major types of plant hormones; auxin, gibberellins, cytokinins, abscisic acid and ethylene etc.

Question 7

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


The movement of leaves of a sensitive plant is touch sensitive and does not depend on the direction of the stimulus and is growth independent. On the other hand, movement of a shoot depends on the direction of light and is known as phototropism. This movement is directional and growth dependent.

Question 8

Give an example of a plant hormone that promotes growth.


Auxins promote stem elongation, growth and movement.

Question 9

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


Auxin increases in concentration in part of the tendril that is away from support. This results in increased cell division in that part. Lesser auxin occurs on the side of contact as compared to the free side. As a result, auxin promotes growth on the free side and the tendrils coil around the support.

Question 10

Design an experiment to demonstrate hydrotropism.


Experiment to demonstrate hydrotropism

Take two small beakers and label them as A and B.

(a) Take a beaker A with water.

(b) 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.

(c) Attach few germinating seeds in the middle of the filter paper bridge.

(d) Now, cover the entire set-up with a transparent plastic container so that moisture is retained.


The roots of germinating seeds will grow towards beaker A.

This experiment demonstrates the phenomenon of hydrotropism.

Question 11

How does chemical coordination take place in animals?


Chemical coordination in animals takes place through hormones. These hormones are chemical messengers. They are secreted by glands and directly released in the bloodstream. The blood carries them to specific tissues or organs called target tissues/organs. In the target, they trigger a biochemical or physiological activity. The hormones are of different types and perform different functions.

Question 12

Why is the use of iodised salt advisable?


Iodine is an important constituent of the hormone thyroxine that regulates carbohydrate, fat and protein metabolism in our body.

If there is a deficiency of this hormone, it may result in enlargement of the thyroid gland. This can lead to goitre, a disease characterized by swollen neck. Therefore we should use iodised salt to avoid deficiency of thyroxine hormone.

Question 13

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


Adrenal gland secretes adrenaline hormone when someone is in an emergency situation. It is secreted directly into the blood and is transported to different parts of a body. It increases the rate of heartbeat and breathing rate, so that more oxygen could be supplied to the muscles. It also increases blood pressure. This enables a person to fight an emergency situation.

Question 14

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


Insulin is a hormone. It plays an important role in sugar metabolism. It converts extra sugar present in the blood into glycogen. Diabetes is caused due to poor or no secretion of insulin by pancreas. Thus, patients suffering from diabetes are given insulin injection to control their blood sugar level.