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Physiology_Ch. 62

Nervous System Control of GI Function

QuestionAnswer
What are the 3 layers of smooth muscle found in the intestinal wall (from superficial to deep)? Longitudinal, circular, and mucosal
What structure is located between the longitudinal muscle layer and the circular muscle layer (located near the outside of the intestinal smooth muscle wall)? Myenteric nerve plexus
What nervous system structure is located in the submucosal layer of the intestinal wall (located closer toward the center lumen)? Meissner's plexus (submucosal nerve plexus)
What is the length and width of the smooth muscle fibers of the GI tract? 200-500 micrometers long and 2-10 micrometers wide
GI smooth muscle fibers are generally in bundles. How many fibers are typically in a bundle? 1000 fibers
What electrically connect each muscle cell in GI smooth muscle? Gap junctions
Each muscle layer is a latticework of bundles. How do these muscle layers function? Function as a syncytium
What are slow waves? Gradual changes in the resting potential of the smooth muscle fibers
What are the slow wave frequencies in the stomach, duodenum, ileum, and colon? Stomach: 3/minute; duodenum: 10-12/minute; ileum: 8-9/minute; colon: 3/minute
What is the myenteric plexus? Chain of interconnected neurons that extends the entire length of the GI tract
What does the myenteric plexus control? Rate and strength of muscle contraction along the length of the gut (peristalsis)
What does the submucosal plexus control? Controls contraction of the submucosal muscles, causing infolding of the mucosa - thus controlling the rate of secretion, absorption, and blood flow
There are numerous neurotransmitters used with respect to the myenteric and submucosal nerve plexuses. Name some of them. Serotonin, dopamine, NO, substance P
The GI tract is under parasympathetic and sympathetic autonomic control. Cranially, parasympathetic innervation is primarily via the __________. Vagus nerve
To what parts of the GI tract does the vagus nerve provide parasympathetic innervation? Primarily to esophagus, stomach, and pancreas, and somewhat less to the small intestine and proximal half of the large intestine
What type of fibers make up most (80%) of the vagus nerve? Afferent fibers
The GI tract is under parasympathetic and sympathetic autonomic control. Caudally, parasympathetic innervation is via the ___________. Pelvic nerves
To what parts of the GI tract do the pelvic nerves provide parasympathetic innervation? Distal half of the large intestine
Where are the post-ganglionic neurons of the GI tract located? Within the myenteric and submucosal plexuses
Are most of the parasympathetic neurons excitatory or inhibitory? Excitatory
Created by: Cory67