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GI final - hormone lecture
n/a
46
Health Care
Graduate
12/13/2009

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Term
what does ghrelin do?
Definition
stimulates food intake via activation of the arcuate nucleus in the hypothalamus serving to counter the appetite suppressant effect of the adipocyte producing hormone leptin
Term
what are the 2 major forms of biologically active gastrin and where are they located?
Definition
G17 and G34. antral gastrin >90% G17. duodenal gastrin 50% G17 and 50% G34
Term
gastrin release is brought about by?
Definition
antral distention, amino acid and peptide exposure, neural stimulation precipitated by sight smell and or taste of food. (microvilli on antral G cells structured to sample luminal contents)
Term
2 things that regulate gastrin release?
Definition
gastric acid in the gastric lumen serves as negative feedback on gastrin release and somatostatin (from antral D cells) acid stimulates somatostatin release, which in turn inhibits gastrin release
Term
when is gastrin release in response to amino acids inhibited?
Definition
when the luminal pH falls below 3
Term
how does somatostatin decrease gastric acid secretion?
Definition
reduction of histamine release from enterochromaffin-like cells as well as directly inhibiting parietal cell acid secretion
Term
how does gastrin induce gastric acid release?
Definition
indirectly: stimulates histamine release from ECL cells in corpus of stomach, which stimulates gastric acid release from parietal cells. direct: gastrin can directly stimulate parietal cells via binding to gastrin/CCK receptors to release gastric acid (plays minor role in gastric acid secretion)
Term
why is diarrhea a common sx of ZES?
Definition
excess gastric secretion and inactivation of digestive enzymes (i.e. lipase) in an acidic milieu
Term
what is the octreotide scan and what does it screen for?
Definition
screens for primary tumors as well as sites of occult metastases. most neuroendocrine tumors have hgih density of somatostatin receptors. administer radioactive labeled octreotide
Term
what does CCK do?
Definition
stimulates pancreatic secretion as well as gallbladder contraction; inhibits gastric emptying (directly: CCK-A receptors located on the pylorus; indirectly: CCK-A receptors on afferent vagal fibers that in turn initiate a decrease in gastric motility); acts as a satiety factor via inhibited gastric motility and interaction with hypothalamus (CCK-A receptors on vagus nerve transmit a sensation of fullness to the hypothalamic satiety center, which terminates feeding behavior); inhibits gastric acid secretion by stimulating somatostatin secretion by antral D cells that have CCK receptors
Term
where is CCK located?
Definition
duodenum contains the highest concentration (stored in I-cells) lesser amts found in distal segments of the intestine and enteric nerves
Term
when is CCK released?
Definition
after exposure to a meal rich in fat and protein
Term
what does secretin do?
Definition
stimulates the release of bicarbonate-rich fluid from the pancreas and biliary tree to provide an alkaline buffering of the acid load entering the small intestine and preventing acidic inactivation of pancreatic enzymes needed for digestion and providing defensive barrier against acid damage of duodenum; inhibits gastric acid secretion; potentiates effect of CCK in stimulating pancreatic enzyme secretion
Term
where is secretin located/stored?
Definition
S cells, scattered thru villous and upper crypt regions of small intestinal mucosa, primarily in the duodenum
Term
secretin is released in response to?
Definition
release of endogenous hcl after a meal
Term
what does glucagon-like-peptide-1 do?
Definition
functions during feeding to stimulate insulin release to lower blood glucose levels (and suppress glucagon secretion); plays a role in inducing postprandial satiety
Term
where is glucagon-like-peptide-1 stored?
Definition
L cells of the distal small bowel
Term
glucagon-like-peptide-1 released in response to?
Definition
meal, particularly a glucose-containing meal (dependent on intraluminal glucose levels)
Term
what does glucose-dependent-insulinotropic polypeptide (GIP) do?
Definition
stimulatory effect on insulin release and synthesis (dependent on circulating glucose levels); amplifies the effect of insulin on target tissues (i.e. stimulating fatty acid synthesis in adipose tissue)
Term
what does glucose-dependent-insulinotropic polypeptide (GIP) do?
Definition
stimulatory effect on insulin release and synthesis (dependent on circulating glucose levels); amplifies the effect of insulin on target tissues (i.e. stimulating fatty acid synthesis in adipose tissue)
Term
what does glucose-dependent-insulinotropic polypeptide (GIP) do?
Definition
stimulatory effect on insulin release and synthesis (dependent on circulating glucose levels); amplifies the effect of insulin on target tissues (i.e. stimulating fatty acid synthesis in adipose tissue)
Term
where is vasoactive intestinal polypeptide stored and released from?
Definition
enteric nerves throughout the GI tract (neuropeptide)
Term
where are VIP receptors found?
Definition
pancreatic acini, pancreatic and biliary ductal epithelial cells, gastric and intestinal epithelial cells, smooth muscle layers (esp sphincters, lower esophageal and internal anal), vascular smooth muscle cells and lymphocytes
Term
what does VIP do?
Definition
pancreatic secretion, control of GI motility, sphincter relaxation, intestinal epithelial secretion, inhibition of gastric acid secretion, modification of immune function and GI blood flow
Term
what controls VIP release?
Definition
vagus nerve
Term
what is watery-diarrhea-hypokalemia-achlorhydria sydnrome? (verner-morrison)
Definition
excess amounts of tumor producing VIP released into circulation with resultant intestinal hypersecretion and depressed acid secretion
Term
where is somatostatin synthesized and secreted from?
Definition
neurons and enteroendocrine D cells
Term
what are somatostatins functions?
Definition
generally inhibitory - inhibits gastric acid secretion, insulin secretion, glucagon secretion, and PP secretion in the endocrine pancreas. inhibits gastrin, secretin, CCK, GIP, VIP and motilin in the GI tract; inhibits gut motility, decreases splanchnic blood flow
Term
what do we use somatostatin as tx for?
Definition
conditions characterized by excess hormone secretion (bc its inhibitory) and tx of neuroendocrine tumors, secretory diarrheas, and acromegaly. also can tx GI bleeding from portal htn bc it reduces splanchnic blood flow. use octreotide (synthetic analogue) bc it has a longer half life
Term
which hormones share the PP fold? and where is each expressed?
Definition
pancreatic polypeptide (endocrine cells), peptide YY (neurons and endocrine cells) and neuropeptide Y (neurons)
Term
what induces PP secretion?
Definition
meal intake - cephalic-vagal phase, gastric phase (released in response to gastric distension), intestinal phase (release in response to fat, AA, glucose in proximal small intestine)
Term
pancreatic polypeptide is produced by?
Definition
PP islet cells (accts for less than 10% of all pancreatic islet cells)
Term
what is the function of pancreatic polypeptide?
Definition
alterations in gastric, intestinal, and pancreatic secretions (decreasing pancreatic exocrine secretion); appetite suppressant. (*high PP plasma levels found in pts with GI endocrine tumors)
Term
PYY is released in response to?
Definition
a meal - fat as the major stimulant altho other nutrients and bile acids stimulate secretion
Term
what is the function of PYY?
Definition
inhibits GI motility, pancreatic and gastric secretion as well as intestinal chloride secretion. contributes to energy homeostasis via an anorectic effect and resultant decreased food intake
Term
PYY release is markedly enhanced in pts with what condition?
Definition
malabsorption - delays gastric emptying and intestinal transit, allows for increased nutrient-mucosal contact time increasing digestive and absorptive efficiency.
Term
whats the ileal brake phenomenon and what hormone mediates it?
Definition
perfusion of ileum with fat slows intestinal transit (mediated by PYY)
Term
functions of neuropeptide Y
Definition
regulation of vascular and cardiac reponses, modulation of circadian rhythm, potent stimulant of feeding; effects on GI tract primarily inhibitory, decreasing intestinal and pancreatic secretions, slowing GI motility and causing splanchnic vasoconstriction
Term
what hormone is in the tachykinin peptide family?
Definition
substance P
Term
where is the concentration of substance P the highest?
Definition
neurons of the esophagus, prox small intestine and colon
Term
what is the function of substance P?
Definition
stimulates esophageal and intestinal peristalsis and pancreatic secretion, increases blood flow in the gut, mediates pain impulses arising from the gut
Term
motilin family located where?
Definition
M cells in the duodenum and proximal jejunum.
Term
when are motilins secreted?
Definition
in cyclical manner that correlates with increased antroduodenal motor activity during the fasting state of the migrating motor complex
Term
what do motilins do?
Definition
accelerates gastric emptying of a meal
Term
which antibacterial drug is a motilin receptor agonist?
Definition
erythromycin
Term
primary function of the tyrosine kinases?
Definition
prominent effects on cell growth, affect cell survival, differentiation and movement. positive impact in tx of patients with malignancies
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