(a) Dendrites
(b) Cyton
(c) Axon
(d) Axon terminals

Figure (a) appears more accurate because it is showing positive geotropic movement in roots and negative geotropic movement in stem.

Iodised salt in diet is advisable because it contains iodine, which is essential element for the synthesis of thyroxine hormone by thyroid gland. In case, iodine is deficient in our diet, there is a possibility of suffering from goitre.

Tropic Movement : It is the movement of plants towards stimulus.
Example - stem growth, root growth, pollen tube growth etc.
nastic Movement : Which the movement of plant is neither towards nor away from the stimulus, it is called nastic movement.
Example : Movement in the leaves of touch me not plants in which leaves fold when touched

The two hormones secreted by pancreas are insulin and glucagon. Insulin converts the sugar present in the blood to glucagon and hence reduces the blood sugar level. Glucagon converts the glycogen into sugar and hence increases the blood sugar level.

(a) Pineal Gland
(b) Pancreas
(c) Adrenal gland
(d) Testis

(a) Auxin
(b) Giberellin
(c) Cytokinin
(d) Abscissic acid

Some diabetes patients are given injections of insulin to fulfil the requirement of insulin in their body. Insulin is a hormone produced by the pancreas and helps in regulating blood sugar levels in our body. If sugar level increases in the blood, due to lack of insulin, it leads to many harmful effects.

Auxins promote cell elongation and are present at the shoot tip. When tendril comes in contact with a support, auxin stimulates faster growth of the cells on the opposite sides. Thus, the tendril coils around the support.

Brain has limited role to play in reflex action. It is an extremely quick action, which does not involve any thinking by the brain. In this type of action, the stimulus is received by the spinal cord that sends a response,e.g. coughing, The action is registered in cercbral brain just for memory.

The differences between a reflex action and walking are as follows:

The function of receptors in our body is very important as they collect informations about changes in the environment around us. Receptors then pass the same information in the form of nerve impulse to the central nervous system, where the information is processed and the ultimate response is given. Now, for example, if the gustatory receptors of our tongue do not work properly, we will not be able to know the taste of different types of foods (whether it is sweet, salty, sour or bitter, etc.)

Plant hormones are organic substances produced naturally in higher plants. They control growth and other physiological functions of the plants. These are required in very small amounts.