Motor neurones are nerves that are directly responsible for controlling the activity of muscle fibres (Fig 1).

The cell body of a motor neurone contains a nucleus, a number of short dendrites that extend outwards, and a single long fibrous axon that extends all the way from the cell body to the muscle. As this axon approaches the muscle, it branches and ends as axon terminals at the neuromuscular junction.

These nerves are classified as Aα fibres, which have the widest diameter of all nerves (12-20 μm). In general, the greater the diameter of a nerve, the greater its speed of conduction. Motor neurones have conduction velocities of around 100 m/s.

The classification of nerve fibre types is shown in Table 1.