GI Hormones Flashcards
3 regulators of GI secretion
- direct from food
- autonomic stimulation
- hormones
parietal cells
secrete H+ and intrinsic factor, found in body and fundus of stomach
ECL cells
secrete histamine, leads to acid secretion
Chief cells or peptic cells
secrete pepsinogen, converted to pepsin at low pH
G cells
secrete gastrin, stimulates acid
found in antrum and pylorus
D cells
secrete somatostatin, suppress gastrin
found near G cells
stimulation of G cells
increases in pH (shuts off D cells)
vagus nerve stimulates GRP in response to food, causes gastrin release
CCK source and fn
from I cells in duodenum/jejunum
contraction of gallbladder, stimulation of pancreatic enzyme secretion, relaxation of sphincter of Oddi
regulation of CCK
w/ food in system, positive feedback loop- stimulated by peptides and fatty acids which are increased by actions of CCK on pancreatic enzymes
stopped when food is in lower GI
secretin source and fn
from S cell in duodenum
stimulates bicarb secretion from pancreas, augments CCK, decreases acid secrtion
regulation of secretin
stimulated by protein digestion and acid, negative feedback loop as it causes fluid to become more alkaline
what must happen at acinar cells and ducts in pancreas to move enzymes and bicarb out
Cl must be moved across membrane, water follows and flushes them out
helped by centroacinar and duct cells
regulation of bicarb secretion in pancreas
secretin helps- activates cAMP which pumps Cl into lumen, moves back across in exchange for bicarb
Na and water follow Cl being moved out, increases amount of fluid
somatostatin inhibits this process
role of vasoactive intestinal peptide
nuerocrine from ENS, stimulates intestinal secretion of electrolytes ad nwater to help motility
relaxes sphincters via NO fomration
motilin source and fn
made by ECL and Mo cells along GI tract, produces MMCs
gastric inhibitory polypeptide (GIP) source and fn
from K cells in duodenum and jejunum
decrease acid secretion, also helps with insulin realease
aka glucose dependent insulinotropic peptide
regulation of GIP
stim by glucose and fatty acids
somatostatin source and fn
from D cells in pancreatic islets, stomach, duodenum
inhibits: gastrin, VIP, GIP, CCK, secretin, motilin
inhibits pancreatic endocrine and exocrine secretion- ie inhibits absorption of glucose, AA, TGs
slows gastric emptying, reduces SM contractions and blood flow in intestine
regulation of somatostatin
stim by acid in lumen
