How are nerve cells adapted to their function?

To answer this question we first need to understand what the function of a nerve cell, or neurone, is. Neurons need to be able to rapidly transmit electrical impulses along their length. They also need to exchange signals with neighbouring neurons across the gaps, known as synapses, that separate them. To acheive these functions, nerve cells have several adaptations. The axon, the long, thin part of the neurone along which the impulse passes, is covered in a fatty myelin sheath, which acts as an electrical insulator. This increases the speed of transmission by forcing the impulse to jump between gaps in the sheath, known as nodes of ranvier, rather than passing along the full length of the axon. Nerve cells also have a lot of mitochondria, which provide the energy to synthesise neurotransmitters such as acetylcholine that pass messages across synpases. In addition, numerous fine extensions to the cell body at one end of the cell, known as dendrites, provide a high surface area allowing the nerve cell to form synapses with many others. Similar branching occurs at the other end of the cell, and synaptic knobs at the end of branches store neurotransmitter, ready to diffuse across the synapse as soon as an impluse arrives.