Receptors and effectors

Receptors

Receptors are groups of specialised cells. They can detect changes in the environment, which are called stimuli, and turn them into electrical impulses. Receptors are often located in the sense organs, such as the ear, eye and skin. Each organ has receptors sensitive to particular kinds of stimulus.

Receptors

sense organs	receptors sensitive to
Skin	touch, pressure, pain and temperature
Tongue	chemicals in food
Nose	chemicals in the air
Eyes	light
Ears	sound and position of the head

The central nervous system - CNS - in humans consists of the brain and spinal cord. When a receptor is stimulated, it sends a signal along the nerve cells - neurones - to the brain. The brain then co-ordinates the response.

Effectors

An effector is any part of the body that produces the response. Here are some examples of effectors:

• a muscle contracting to move the arm
• a muscle squeezing saliva from the salivary gland
• a gland releasing a hormonehormone: chemical messengers produced in glands and carried by the blood to specific organs in the body into the blood