Question

When we touch a hot plate unknowingly, then this heat is sensed by a receptor P present in our fingers. The receptor triggers and impulse in neuron Q which transmits the message to an organ R which is a part of the central nervous system. Here the impulse is passed on to a neuron S which in turn passes it to a yet another neuron T. The neuron T passes the impulse to a tissue U in our arm. The tissue U then contracts and pulls our hand away from the hot plate.
(a) What is the name of (i) receptor P (ii) neuron Q, and (iii) organ R?
(b) What is (i) neuron S, and (ii) neuron T?
(c) Name the tissue U.
(d) What name is given to the phenomenon in which hand is pulled away quickly from the hot plate?
(e) Name the effector in this whole process.

Answer 1

(a) (i) P is a thermoreceptor.
(ii) Q is a sensory neuron.
(iii) R is the spinal cord.

(b) (i) S is a relay neuron. The impulse from the spinal cord is passed on to a relay neuron.
(ii) T is a motor neuron. From the relay neuron, the impulse is passed on to a motor neuron.

(c) U is a muscle.

(d) Reflex action is the phenomenon in which the hand is pulled away quickly from a hot plate. It is performed automatically by an individual.

(e) The effector organ is the muscle of the arm.