PSYC340 Study Guide - Final Guide: Myenteric Plexus, Submucous Plexus, Pelvic Splanchnic Nerves

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1. Describe the nerve supply of the GI tract.
A. Neural innervation of GI tract
A.I. Enteric nervous system (ENS)
A.II. It consists of about 100 million neurons that extend from the esophagus
to the anus. The neurons of the ENS are arranged into two plexuses: the
myenteric plexus and submucosal plexus
A.III. Myenteric plexus (plexus of Auerbach)
A.IV. The myenteric plexus, or plexus of Auerbach, is located between the
longitudinal and circular smooth muscle layers of the muscularis.
A.V. Because the motor neurons of the myenteric plexus supply the
longitudinal and circular smooth muscle layers of the muscularis, this
plexus mostly controls. GI tract motility (movement), particularly the
frequency
A.VI. Submucosal plexus (plexus of Meissner)
A.VII. Is found within the submucosa. The plexuses of the ENS consist of motor
neurons, interneurons, and sensory neurons
A.VIII. The motor neurons of the submucosal plexus supply the secretory cells of
the
mucosal epithelium, controlling the secretions of the organs of the GI
tract. The interneurons of the ENS interconnect the neuron of the
myenteric and submucosal plexuses
A.IX. Autonomic nervous system
A.X. Although the neurons of the ENS can function independently, they are
subject to regulation by the neurons of the autonomic nervous system.
The vagus (X) nerves supply parasympathetic fibers to most parts of the
GI tract, with the exception of the last half of the large intestine, which is
supplied with parasympathetic fibers from the sacral spinal cord. The
parasympathetic nerves
that supply the GI tract form neural connections with the ENS.
Parasympathetic preganglionic neurons of the vagus or pelvic splanchnic
nerves synapse with parasympathetic postganglionic neurons located in
the myenteric and submucosal plexuses. Some of the parasympathetic
postganglionic neurons in turn synapse with neurons in the ENS; others
directly innervate smooth muscle and glands within the wall of the GI
tract.
A.XI. In general, stimulation of the parasympathetic nerves that innervate the
GI tract causes an increase in GI secretion and motility by increasing the
activity of ENS neurons. Sympathetic nerves that supply the GI tract arise
from the thoracic and upper lumbar regions of the spinal cord. Like the
parasympathetic nerves, these sympathetic nerves form neural
connections with the ENS. Sympathetic postganglionic neurons synapse
with neurons located in the myenteric plexus and the submucosal plexus
A.XII. In general, the sympathetic nerves that supply the GI tract cause a
decrease in GI secretion and motility by inhibiting the neurons of the ENS.
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