Enteric nervous system

The digestive tract has its own nervous system, called the enteric (enteric = gut) nervous system, sometimes called the "brain of the gut." It is composed mostly of two large plexuses: the submucosal plexus and myen­teric plexus.

The submucosal plexus, or Meissner's plexus, is located within the submucosal layer. It includes sensory and motor neurons, and postganglionic fibers of both the sympathetic and parasympathetic nervous system. It regulates the activity of glands and smooth muscle in the mucosa.

The myenteric plexus, or plexus of Auerbach, is located between the two layers of smooth muscle fibers in the muscularis externa. These neurons coor­dinate the frequency and strength of digestive tract motility. Therefore, this plexus controls patterns of peristalsis and segmentation through automatic local reflex arcs.

The enteric nervous system also communicates with the central nervous system via afferent visceral fibers of the sympathetic and parasympathetic branches of the autonomic nervous system. The autonomic nervous system also exerts extrinsic control over the functions of the digestive tract. Parasympathetic input generally enhances digestive functions, whereas sym­pathetic input inhibits these functions.