Neurones

Neurones are nerve cells. They carry information as tiny electrical signals. There are three different types of neurones, each with a slightly different function.

1. Sensory neurones carry signals from receptors [receptors: organs which recognize and respond to stimuli ] to the spinal cord and brain.
2. Relay neurones carry messages from one part of the CNS [CNS: Central Nervous System (brain and spinal cord). ] to another.
3. Motor neurones carry signals from the CNS [CNS: Central Nervous System (brain and spinal cord). ] to effectors.

The diagram below shows a typical neurone - in this case, a motor neurone. It has tiny branches at each end and a long fibre carries the signals.

A motor neurone

Synapses

Where two neurones meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals. One neurone releases the chemical into the gap. The chemical diffuses across the gap and makes the next neurone transmit an electrical signal.