Question #238

The sympathetic nervous system consists of pre-ganglionic fibres that arise from the thoracic and lumbar spinal cord (T1-L2). These fibre are myelinated and run to the sympathetic chain which lies adjacent to the vertebral column and extends along its length (also known as the paravertebral chain). From here the pre-ganglionic neurones can do 1 of 4 things:

1. Synapse at the same level
2. Pass proximally or distally along the sympathetic chain before synapsing
3. Continue and synpase at the prevertebral plexus
4. Continue directly to the adrenal medulla (not forming post-ganglionic fibres).

The post-ganglionic neurones are unmyelinated.

In the abdomen the pre-ganglionic neurones do not synpase in the sympathetic chain but rather pass to the coeliac or mesenteric ganglia (also known as the prevertebral ganglia). Post-ganglionic fibres are then carried to target organs on splanchnic nerves:

• Greater splanchnic nerve carries fibres to foregut structures
• Lesser splanchnic nerve carries fibres to midgut structures
• Least splanchnic nerve carries firbes to hindgut structures

Any comments or corrections? Please e-mail help@cambridgequestions.co.uk