The conditions inside our body must be carefully controlled if the body is to function effectively. The conditions are controlled in two ways with chemical and nervous responses.
All control systems include:
Nerve cells are called neurones. They are adapted to carry electrical impulses from one place to another.
A bundle of neurones is called a nerve.
There are three main types of neurone: sensory, motor and relay.
They have some features in common:
Information from receptors passes along neurones, as electrical impulses to co-ordinators such as the central nervous system or CNS. The CNS is the brain and spinal cord. Muscles contracting or glands secreting hormones are the response of effectors coordinated by the CNS.
Stimulus → receptor → coordinator → effector → response
The diagram summarises how information flows from receptors to effectors in the nervous system.
Receptors are groups of specialised cells. They detect a change in the environment (stimulus) and stimulate electrical impulses in response. Sense organs contain groups of receptors that respond to specific stimuli.
|Skin||Touch, temperature and pain|
|Tongue||Chemicals (in food and drink, for example)|
|Nose||Chemicals (in the air, for example)|
|Ear||Sound and position of head|
Effectors include muscles and glands - that produce a specific response to a detected stimulus.