Neurones and Synapses

To communicate between receptors and effectors the body uses two main methods.

These are:

nerves
hormones.

A neurone is a specialised cell that is adapted to pass electrical impulses.

Each neurone has a small diameter so many can fit into one nerve. There are 3 types of neurones

1. Sensory – carry signals from sense organs (receptors) to the brain (CNS: Central Nervous System)

2. Relay – they pass messages between neurones in the CNS.

3. Motor – carry signals from CNS to muscles (effectors)

Although all neurones have different shapes, they all have certain features in common:

One or more long projections from the cell body to carry the impulse a long distance.
A fatty covering (myelin sheath) around the projection for insulation.
Many fine endings (dendrites) so that the impulse can be passed on to many cells.

KEY POINT: Exam questions often ask how neurones are adapted for their job.

The Structure of a Neurone

Sensory Neurone

Motor Neurone

Synapse

Each neurone does not directly end on another neurone. There is a small gap between the two neurones called a synapse. In order for an impulse to be generated in the next neurone, a chemical transmitter is released. This then diffuses across the small gap.

Many drugs work by interfering with synapses. They may block or copy the action of neurotransmitters in certain neurones.

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