Brain and spinal cord = Central nervous system (CNS)
Nerves = peripheral nervous system
There are 3 main types of cells (neurones), each with specific functions:
|
Sensory |
“input” |
RECEPTORS receive information (usually from surroundings), & generate a nervous impulse which passes along the “fibre” out of the cell |
|
Relay/connective |
“processing” |
Take information from sensory neurone, (process it) and may pass impulse on to motor neurone. |
|
Motor |
“output” |
Pass impulse along fibre to other organs (muscles or glands): EFFECTORS |
Nerves are a mixture of fibres of sensory and motor neurones, i.e. 2 types – with impulses moving in each direction.
However in each type of neurone the impulse is unidirectional. No impulse passes back to the sensory neurone, nor from the muscle to the motor neurone.