What nerves are involved in the sympathetic innervation of the pancreas?

The sympathetic innervation of the pancreas is primarily mediated by the lesser and greater splanchnic nerves. These nerves arise from the thoracic spinal cord and carry sympathetic fibers that provide autonomic regulation to various abdominal organs, including the pancreas.

The greater splanchnic nerve typically originates from T5 to T9 spinal levels and mainly innervates the celiac plexus, which supplies many abdominal organs. The lesser splanchnic nerve comes from T10 to T11 levels and can also contribute to the celiac plexus and subsequently the innervation of the pancreas. This is important for regulating processes such as the secretion of pancreatic enzymes and insulin, especially during the 'fight or flight' response where sympathetic activity is increased.

In contrast, the vagus nerve is part of the parasympathetic nervous system, which promotes digestion and insulin secretion, rather than the sympathetic response. The pelvic nerves are also associated with the parasympathetic system, focusing on the lower colon and pelvic organs. The celiac plexus does involve sympathetic nerves, but it is more of a network through which these sympathetic nerves, like the splanchnic, relay their signals. Finally, the phrenic nerve primarily innervates the diaphragm and