Write down the following in the correct order for a simple reflex arc:

(a) impulse travels in motor fibre

(b) impulse travels in sensory fibre

(c) effector organ stimulated

(d) impulse crosses synapse

There are two similar glands P which are located on the top of two similar organs Q in the human body. The glands P are often called glands of emergency and they secrete a hormone R into the blood stream. The hormone R is secreted in large amounts when a person is frightened. It brings about temporary changes in the body which allow a lot of substance S from the liver to go into blood so as to provide a lot of energy in a very short time. This helps the person concerned to fight back or run away from the frightening situation. What are P, Q, R and S?

The two glands A and B which occur in pairs, are present in the endocrine system of humans. The �pair of glands A is found only in females whereas the pair of glands B occurs only in males. The glands A make and secrete two hormones C and D whereas glands B make and secrete only one hormone E. In addition to hormones, glands A make gametes F whereas glands B make gametes G.

(a) What are glands A?

(b) What are hormones C and D?

(c) What are glands B? Name the hormone E.

(d) What are gametes (i) F, and (ii) G?

(e) Which event in the life of males and females is associated with the secretion of hormones C, D and E?

The organ A which is located inside the skull of our body is protected by a bony box Band it is surrounded by three membranes C. The space between the membranes is filled with a liquid D which protects the organ A from mechanical shocks. The organ A in combination with another organ E makes up the central nervous system.

(a) What is organ A?

(b) What are (i) B (ii) C, and (iii) D ?

(c) Name the organ E.

(d) While walking barefooted, if we happen to step on a sharp piece of stone, we immediately lift our foot up. Which of the two organs, A or E, is directly involved in this action?

(e) If we step out from a darkened room into bright sunshine, we close our eyes for a moment. Which of the two organs, A or E, is directly involved in this action?

Explain why, the tongue may be considered to be both a receptor and an effector organ.