CoachA neuron is a cell specialised for signalling: a cell body with its nucleus, branching dendrites that receive signals, and a single long fibre, the axon, that carries the neuron’s own signal to its endings — for a motor neuron of the leg, a metre away. Many axons are wrapped in a fatty sheath, myelin, laid down by companion cells, which speeds conduction. A nerve is a bundle of hundreds or thousands of axons.
