Fig 1 shows the PNS and SNS divisions of the central nervous system. Point to either heading to reveal the processes controlled by that division.

The SNS supplies all parts of the body, including the trunk and limbs, but the PNS supplies the viscera only (except the adrenal glands and gonads, which only receive a sympathetic supply).

The efferent pathways for both the SNS and PNS consist of two sets of neurones, 'preganglionic' and 'postganglionic', that synapse in an intermediary ganglion.

The cell bodies of the preganglionic neurones are in the brain or spinal cord. Their axons are myelinated slow conducting B fibres.

Each preganglionic cell anastomoses with 8-9 postganglionic cells to produce the diffuse responses characteristic of the ANS. The axons of the postganglionic neurones are mainly unmyelinated C fibres.