Term
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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 |
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Term
| what are the 2 major forms of biologically active gastrin and where are they located? |
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Definition
| G17 and G34. antral gastrin >90% G17. duodenal gastrin 50% G17 and 50% G34 |
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Term
| gastrin release is brought about by? |
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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) |
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Term
| 2 things that regulate gastrin release? |
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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 |
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Term
| when is gastrin release in response to amino acids inhibited? |
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Definition
| when the luminal pH falls below 3 |
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Term
| how does somatostatin decrease gastric acid secretion? |
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Definition
| reduction of histamine release from enterochromaffin-like cells as well as directly inhibiting parietal cell acid secretion |
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Term
| how does gastrin induce gastric acid release? |
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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) |
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Term
| why is diarrhea a common sx of ZES? |
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Definition
| excess gastric secretion and inactivation of digestive enzymes (i.e. lipase) in an acidic milieu |
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Term
| what is the octreotide scan and what does it screen for? |
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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 |
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Term
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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 |
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Term
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Definition
| duodenum contains the highest concentration (stored in I-cells) lesser amts found in distal segments of the intestine and enteric nerves |
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Term
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Definition
| after exposure to a meal rich in fat and protein |
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Term
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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 |
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Term
| where is secretin located/stored? |
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Definition
| S cells, scattered thru villous and upper crypt regions of small intestinal mucosa, primarily in the duodenum |
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Term
| secretin is released in response to? |
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Definition
| release of endogenous hcl after a meal |
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Term
| what does glucagon-like-peptide-1 do? |
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Definition
| functions during feeding to stimulate insulin release to lower blood glucose levels (and suppress glucagon secretion); plays a role in inducing postprandial satiety |
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Term
| where is glucagon-like-peptide-1 stored? |
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Definition
| L cells of the distal small bowel |
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Term
| glucagon-like-peptide-1 released in response to? |
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Definition
| meal, particularly a glucose-containing meal (dependent on intraluminal glucose levels) |
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Term
| what does glucose-dependent-insulinotropic polypeptide (GIP) do? |
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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) |
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Term
| what does glucose-dependent-insulinotropic polypeptide (GIP) do? |
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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) |
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Term
| what does glucose-dependent-insulinotropic polypeptide (GIP) do? |
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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) |
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Term
| where is vasoactive intestinal polypeptide stored and released from? |
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Definition
| enteric nerves throughout the GI tract (neuropeptide) |
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Term
| where are VIP receptors found? |
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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 |
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Term
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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 |
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Term
| what controls VIP release? |
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Definition
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Term
| what is watery-diarrhea-hypokalemia-achlorhydria sydnrome? (verner-morrison) |
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Definition
| excess amounts of tumor producing VIP released into circulation with resultant intestinal hypersecretion and depressed acid secretion |
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Term
| where is somatostatin synthesized and secreted from? |
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Definition
| neurons and enteroendocrine D cells |
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Term
| what are somatostatins functions? |
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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 |
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Term
| what do we use somatostatin as tx for? |
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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 |
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Term
| which hormones share the PP fold? and where is each expressed? |
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Definition
| pancreatic polypeptide (endocrine cells), peptide YY (neurons and endocrine cells) and neuropeptide Y (neurons) |
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Term
| what induces PP secretion? |
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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) |
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Term
| pancreatic polypeptide is produced by? |
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Definition
| PP islet cells (accts for less than 10% of all pancreatic islet cells) |
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Term
| what is the function of pancreatic polypeptide? |
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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) |
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Term
| PYY is released in response to? |
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Definition
| a meal - fat as the major stimulant altho other nutrients and bile acids stimulate secretion |
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Term
| what is the function of PYY? |
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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 |
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Term
| PYY release is markedly enhanced in pts with what condition? |
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Definition
| malabsorption - delays gastric emptying and intestinal transit, allows for increased nutrient-mucosal contact time increasing digestive and absorptive efficiency. |
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Term
| whats the ileal brake phenomenon and what hormone mediates it? |
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Definition
| perfusion of ileum with fat slows intestinal transit (mediated by PYY) |
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Term
| functions of neuropeptide Y |
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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 |
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Term
| what hormone is in the tachykinin peptide family? |
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Definition
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Term
| where is the concentration of substance P the highest? |
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Definition
| neurons of the esophagus, prox small intestine and colon |
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Term
| what is the function of substance P? |
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Definition
| stimulates esophageal and intestinal peristalsis and pancreatic secretion, increases blood flow in the gut, mediates pain impulses arising from the gut |
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Term
| motilin family located where? |
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Definition
| M cells in the duodenum and proximal jejunum. |
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Term
| when are motilins secreted? |
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Definition
| in cyclical manner that correlates with increased antroduodenal motor activity during the fasting state of the migrating motor complex |
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Term
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Definition
| accelerates gastric emptying of a meal |
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Term
| which antibacterial drug is a motilin receptor agonist? |
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Definition
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Term
| primary function of the tyrosine kinases? |
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Definition
| prominent effects on cell growth, affect cell survival, differentiation and movement. positive impact in tx of patients with malignancies |
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