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24 Cards in this Set
- Front
- Back
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The GI tract is innervated by two sets of nerves
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Extrinsic nervous system
Intrinsic nervous system |
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Para innervation to the 2/3 of transverse colon increases
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GI secretions and motility
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Parasymp..afferent fibers picked up cues at
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chemoreceptors, osmoreceptors and mechanical receptors in the mucosa
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Sympathetic Innervation to gut comes from
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1) Celiac Ganglia
2)SMA ganglia 3) IMA ganglia |
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Symp innvervation to the gut effect
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Slows down digestion
Sympathetic stimulation inhibits secretion and motility Divert blood flow away from the GI tract Accelerator: Fight or Fight |
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Does the enteric system need input from CNS?
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no
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do mechanoreceptors and chemoreceptors in the muscularis mucosa need cns input?
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no
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Where do parasymp preganglionics synapse in the gut?
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at the wall of the GI tract
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Where do symp preganglionics synapse in the gut?
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outside the GI wall
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What type of fibers (para and symp) reach the GI wall?
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Para=Preganglionics
Symp=Postganglionics |
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Primary symp preganglionic neurotransmitter
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Ach and it's also the major postganglionic parasymp that regulates secretory function and smooth muscle activity
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Primary postganglionic symp neurotransmitter is
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NE and causes vasoconstriction and relaxes intestinal muscle contractions
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Vasoactive Intestinal Peptide (VIP) inhibits
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intestinal muscle contractions and stimulates fluid and electrolyte secretion.
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Gastrin-releasing peptide is a neurotransmitter made in the ENS that stimulates
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Gastrin secretion
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ENS function can be modified by CNS via
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autonomic centers in the medulla
Vagovagal reflex |
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an example of how GI is under control of cerebral centers of CNS
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The increase in gastric secretion by the sight or the smell of food
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ENS possesses multiple programmed responses
Efferent response to several stimuli is often quite similar The responses to: distention of the jejunum and bacterial enterotoxin are the same |
Stimulation of profuse fluid
Propagated smooth-muscle contractions |
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Vasovagal reflex example, gastric receptive relaxation reflex
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The distention of the stomach results in relaxation of the smooth muscle allowing filling of the stomach to occur. This means that volume in the stomach goes up pressure stays the same and tone of muscle is under control of nervous system. W/o this reflex stomach would burst
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Immune cells role in regulation
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via mast cells, they communicate signals from neurons to target cells
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Immune cells secrete____to affect target cells
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histamine
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Brain gut axis has 3 essential components
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ENS
GI hormones Immune system |
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Brain gut axis is a bidirectional system because
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CNS can influence GU and viceversa.
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Brain-Gut axis provides substantial redundancy
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Refinement of the regulation of digestive processes
Backup or fail-safe mechanisms |
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Hirschsprung's disease manifests as and is caused by
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severe chronic constipation in infancy or failure to pass meconium at birth
-Absence of Myentric and submucosal plexus in the distal part of the colon and the rectum |
