(a) Receptor: A receptor is a cell (or a group of cells) in a sense organ which is sensitive to a particular type of stimulus (or a particular type of change in the environment).

Example: Photoreceptors and Phonoreceptors.

Effector: An effector is the part of the body which can respond to the stimulus according to the instructions sent from the nervous system (spinal cord and brain).

Example: Muscles and glands.

(b) Cerebrum:

(i) It is a part of forebrain.

(ii) It is the main thinking part of the brain. All our thoughts, sensation, actions and movements are controlled by cerebrum.

Cerebellum:

(i) It is a part of hindbrain.

(ii) It helps in maintaining posture and balance of the body. It enables us to make precise and accurate movements.