The nervous system allows the body to respond to changes in the environment. In humans it consists of:
The Central Nervous System (CNS) refers to the first two of these, i.e. the brain and spinal cord.
There are two ways in which the nervous system handles these changes, depending on how urgently a reaction is needed:
Stimuli are things that set off a reaction in the nervous system - for example, light, heat, sound, gravity, smell, taste, or temperature. The singular is stimulus.
Now look at the following sub-topics:
[ This page has been adapted from www.bbc.co.uk/schools/gcsebitesize/science