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:
They have some features in common:
Where two neurones meet there is a small gap called a synapse. Here the electrical signal must be converted into a chemical one, which is converted back to an electrical one on the other side of the synapse where the next neurone starts.
Receptor cells detect a change in the environment (a stimulus) and start electrical signals along neurons. These move towards the central nervous system (CNS). The CNS is the brain and spinal cord. It coordinates the responses. Messages are then sent back along different neurones to muscles which contract or relax, and glands which secrete hormones. Muscles and glands are called effectors.
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 and stimulate electrical impulses in response. Sense organs contain groups of receptors that respond to specific stimuli.
|Tongue||Chemicals (in food and drink, for example)|
|Nose||Chemicals (in the air, for example)|
Effectors include muscles and glands. They produce a specific response to a detected stimulus. For example: