The of the internal conditions of a to maintain conditions for , in response to internal or external .

Controlled internal conditions include:
-
-
-

Receptors:
cells that
may be in the or

Coordination centres:
areas that from receptors
includes the , and

Effectors:
that bring about response
respond to received stimulus
restore conditions to optimum through changes

The nervous system carries impulses between metres per second

Stimulus

|
Receptor

| ()

Coordinator ( )

| ()

Effector
( may contract
may secrete chemicals )

The sends an impulse along a , carrying information about a change in the environment to the coordinator (). Once all incoming information has been processed, the coordinator sends an impulse along the , which stimulate the needed in a particular circumstance.

Experiments to measure reaction times:
- ( reaction to visual stimulus )
- hand squeeze around circle ( )