(a) A receptor is an organ or cell able to respond to heat, light or other external stimulus and transmit a signal to a sensory nerve.

An effector is a muscle, gland or an organ capable of responding to a stimulus, especially a nerve impulse.

(b) Cerebrum, a part of the forebrain, is responsible for controlling our thoughts, sensations, actions and movements.

Cerebellum, a part of the hindbrain, is responsible for maintaining the body posture and balance of the brain.