The innervation of the pancreas is provided by the autonomic nervous system via the parasympathetic and sympathetic nerve fibers.

Parasympathetic innervation

The parasympathetic innervation of the pancreas mainly comes from the posterior vagal trunk of the vagus nerve (CN X). The posterior vagal trunk is larger than the anterior vagal trunk, and it is composed of fibers from the right vagus nerve. The parasympathetic fibers that innervate the pancreas originate from the dorsal motor nucleus of the vagus nerve found in the brainstem. Parasympathetic fibers provide secretomotor effects.

Sympathetic and parasympathetic fibers are scattered throughout the pancreas, also reaching the pancreatic acinar cells. The activation of the parasympathetic nervous system affects both the exocrine and endocrine portions of the pancreas. Therefore, it results in the production and release of pancreatic juice, insulin, and glucagon.

Sympathetic innervation

The sympathetic innervation of the pancreas comes from the interomediolateral column of the spinal cord, and it reaches the pancreas via the greater thoracic splanchnic nerves and lesser thoracic splanchnic nerves. Sympathetic innervation is provided by the T5 (T6) - T12 (T10) thoracic splanchnic nerves. Nerve fibers travel to the celiac plexus and the superior mesenteric plexus, where they synapse and further reach the pancreas.

The sympathetic system provides slightly opposite effects to the parasympathetic nervous system. Sympathetic fibers provide vasoconstriction (narrowing of the blood vessels), and they inhibit the release of insulin while stimulating the release of glucagon. Sympathetic fibers have little or no effect on ductal and acinar cell secretions. The sympathetic nervous system affects more the function of the endocrine portion and, to a lesser extent, the exocrine part of the pancreas.

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Innervation of pancreas