1. Receptors are biological transducers that convert energy from both external and internal environments into electrical impulses. They may be massed together to form a sense organ, such as the eye or ear, or they may be scattered, as are those of the skin and viscera. Receptors are connected to the central nervous system by afferent nerve fibres.
2. Effector organ is a part of the body that responds to a stimulus and a stimulus is a change in the environment that is detected by a receptor.
Explanation: