Autonomic Innervation of Small Intestine

At the anorectal junction, the autonomic innervation gives way to somatic innervation.

AUTONOMIC SYSTEM ROLE IN GUT MOTILITY

The enteric nervous system (ENS) is a complex network of neurons and nerve fibers located within the gut wall and consist of the two ganglionic strata: the myenteric, or Auerbach plexus between the two layers of the external muscle, and the submucosal Meissners plexus, which extends from the esophagus to the anal canal and is responsible for peristaltic activity, secretion of mucosal glands, vasoconstriction and vasodilation, water absorption, and electrolyte balance. The parasympathetic and sympathetic exert external regulatory influences on the ENS. The cholinergic terminals of the parasympathetic system, acting on the smooth muscles of the small and large intestine and also via the enteric plexuses, cause increased motility of the intestine and increased secretory activity of the glands. Postganglionic fibers of the sympathetic nervous system release norepinephrine, causing decreased motility.

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