Phys DSA Flashcards
What are the 7 GI tract sphincters?
- upper esophageal sphincter
- lower esophageal sphincter
- pylorus
- sphincter of ODDI
- Ileocecal valve
- internal anal sphincter
- external anal sphincter
What are the functional layers of the intestinal wall?
Mucosa
Submucosa
Muscularis Externa
Serosa
Which layers contain the enteric nervous system
submucosa - submucosal plexus
muscular - myenteric plexus
What is the GI tract innervated by?
extrinsic autonomic nervous system
What does the ENS do?
controls contraction, secretion and endocrine function of the GI tract
Where does the ENS receive information from?
parasympathetic and sympathethic nervous system, CNS, and sensory information from mechanoreceptors and chemoreceptors
What is the vago-vagal reflex?
A reflex that controls contraction of the gastrointestinal muscle layers in response to distension of the tract by food.
Which center controls food intake?
the brain
Which parasympathetic nerves modulate GI function?
Vagal and pelvic
In the PNS, where are preganglionic nerve cell bodies located? postganglionic?
pregang - brainstem or spinal cord
postgant - wall of organ
What is the synapse between pre and post ganglionic cells in the PNS?
nAChRs
How does the SNS modulate GI function?
by preganglionic efferents that that run between the spinal cord and prevertebral ganglia, and postganglionic fibers from those ganglia to the myenteric and submucosal plexuses
What do preganglionic efferents release? What do postganglionic efferents release?
ACh; NE
What is somatostatin secreted by? What is their effect?
D cells; decrease luminal pH
How does somatostatin increase pH?
inhibits gastric H secretion and secretion of other GI hormones; responds to low pH
Where is somatostatin secreted outside of the GI tract?
hypothalamus and delta cells of the exocrine pancreas
What cells secrete histamine in the stomach?
it is stored and secreted by enterchromaffin-like (ECL) cells
What is the target of histamine?
parietal cells to stimulate acid production
How do enteroendocrine cells function?
they contain secretory granules filled with hormones that are released into the the blood stream upon stimulation
What does gastrin do?
increases gastric H secretion and stimulates growth of gastric mucosa
What does CCK do?
increases pancreatic enzyme secretion, increases pancreatic bicarb secretion
stimulates contraction of the gallbladder and relaxation of the sphincter of oddi
stimulates growth of the exocrine pancreas and gallbladder
inhibits gastric emptying
What does secretin do?
increase pancreatic bicarb secretion
increase biliary bicarb secretion
inhibits trophic effects of gastrin on gastric mucosa
What does GIP do?
increases insulin secretion of pancreatic beta cells
decreases H secretion
What does ACh do?
contraction of SM in wall; relaxation of sphincters
increases salivary, gastric and pancreatic excretion
what does NE do?
relaxes SM in wall, contracts sphincters,
increases salivary secretion
what does vasoactive intestinal peptide do?
relaxes SM in wall
increases intestinal and pancreatic secretion
what does NO do?
relaxes smooth muscle
What does GRP do?
increases gastric secretions
What do enkephalins do?
contract smooth muscle
decrease intestinal secretion
What does neuropeptide Y do?
relaxes smooth muscle
decreases intestinal secretion
What does substance P do?
contracts smooth muscle
increases salivary secretion
What is the incretin effect?
The concept that oral nutrient (glucose) administration promotes a much greater degree of insulin secretion compared to a parenteral isoglycemic glucose infusion (IV)
