(a) There are five sense organs in our body. They are the eyes, the ears, the nose, the tongue and the skin.
(b) A receptor is a cell present in the sense organs that is sensitive to specific stimuli.
Example: The eyes have light receptors which can detect light and the ears have sound receptors which can detect sound.
An effector is a part of body which can respond to a stimulus according to the instructions given from the nervous system.
Example: Muscles and glands of the human body.