GI Hormones

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Satiety hormones:

CCK, glucagon like peptide 1, peptide YY

What is the source of somatostatin?

D cells in stomach and duodenum, delta cells of pancreatic islets

Where is somatostatin released?

D cells of stomach and duodenum, delta cells of pancreatic islets

Where is glucagon like peptide 1 released from?

EEC cells in the gut wall

What is the source of VIP?

ENS neurons

What is the target for gastrin releasing peptide?

G cells in antrum of stomach

What cell secretes CCK?

I cells

Where is cholecystokinin released from?

I cells in duodenum and jejunum neurons in ileum and colon

What is the source of GIP?

K cells in duodenum and jejunum

Where is gastric inhibitory peptide released from?

K cells in duodenum and jejunum

Where is secretin released from?

S cells in small intestine

What stimulates relaxation on caudal side during peristalsis?

VIP and NO

What stimulates contraction on orad side during peristalsis?

acetylcholine, substance P

Starch digesting enzyme:

amylase

What is glucagon like peptide 1 involved in regulating?

blood glucose levels via insulin secretion stimulation reduction of appetite and food intake delays in gastric emptying

What is the purpose of peptide YY in the pancreas?

decrease enzyme and fluid secretion

What is the action of secretin on the stomach?

decrease gastric acid secretion

What is the action of peptide YY in the stomach?

decrease vagally mediated acid secretion

What are the actions of gastrin inhibitory peptide?

decreased fluid absorption (exocrine) increased insulin release (endocrine)

Nucleases:

deoxyribonuclease and ribonuclease

What types of stimuli regulate timing of secretions from dueodenum?

distension, presence of protons in chyme, high osmolarity of chyme (due to increased glucose, I think), presence of various macromolecules in lumen

What is the action of gastrin releasing peptide?

don't overthink this - its to increase gastrin release

What is the source of neurotensin?

endocrine cells in ileum

What is the source of peptide YY?

endocrine cells in ileum and colon

Where is peptide YY released from?

endocrine cells in ileum and colon

Where is motilin released from?

endocrine cells in upper GI tract

What type of peptidase is chymotrypsinogen, and what are its products?

endopeptidase, oligopeptides

What type of peptidase is proelastase, and what are its products?

endopeptidase, oligopeptides

What type of peptidase is trypsin, and what are its products?

endopeptidase, oligopeptides

What type of peptidase is typsinogen, and what are its products?

endopeptidase, oligopeptides

What releases 5HT in the colon?

enterochromaffin cells

What are the targets of motilin?

esophageal sphincter, stomach, and duodenum

What type of peptidase is procarboxypeptidase A and B, and what are its products?

exopeptidases, single amino acids (A-neutral, B-basic)

Bile performs what fuctions:

forms micelles to shield hydrophobic aspects of lipid digestion to make them more soluble bile acids act as detergents

Chief cells release large quantities of _________ __________ which adsorbs to the surface of _________ ___________.

gastric lipase, lipid droplets

What does activation of intrinsic neurons in the gastric phase lead to?

gastrin releasing peptide - which leads to release of gastrin from G cells

Where is guanylin released from?

ileum and colon

What is the action of secretin in the pancreas?

increase HCO3 and fluid secretion by pancreatic ducts

What is the action of motilin?

increase smooth muscle contraction (increase GI motility)

What is the action of guanylin?

increased fluid absorption

Lipid digesting enzymes or precursors:

lipase, nonspecific esterase, prophospholipase A2

What cell releases secretin and with what stimulus?

low duodenal pH stimulates release from S cells

What is responsible for phase 3 contractions (between meals) with the migrating motor complex?

motilin

What gland increases acid and pepsin?

oxyntic gland

What is the target organ for gastric inhibitory peptide?

pancreas

What are the target organs for cholecystokinin?

pancreas and gallbladder

What are the targets of secretin?

pancreas and stomach

What are the three lipases found in duodenal pancreatic juice?

pancreatic lipase, phospholipase A2, cholesterol esterase

What are the five very general products of pancreatic acinar cells?

precursors of proteases, starch digesting enzymes, lipid digesting enzymes and precursors, nucleases, regulatory factors

What is glucagon like peptide 1 secreted in response to?

presence of luminal carbohydrates and lipids

Regulatory factors:

procolipase, trypsin inhibitors, monitor peptide

Macronutrients in chyme, when delivered to duodenum, lead to what?

release of pancreatic and biliary secretions, and the activation of hormonal, paracrine, and neural pathways regulating gastric emptying

What is CCK(B) receptors sensitive to, and where are they found?

responsive to gastrin and CCK, and found on parietal cells

What hormone triggers release of bicarb from pancreas?

secretin

What three factors mediate the pressure gradient from the stomach to the duodenum?

serotonin, NO, NE

What duodenal feedback is elicited when chyme enters?

slowed gastric emptying (vagal), CCK released, gallbladder contraction (CCK), pancreatic secretion, relaxation of sphincter of Oddi (CCK)

What are the targets of guanylin?

small and large intestine

Secretions into the GI tract are regulated by the opening and closing of:

sphincter of Oddi

What are the actions of cholecystokinin?

stimulate enzyme secretion and contraction

Peptide YY stimulation and actions:

stimulated by presence of lipids in lumen, leads to inhibition of Cl- burst and thus fluid secretion -> slows propulsion to allow more time for digestion and absorption in ileum

What is the chain of events once secretin is released?

stimulates secretion of bicarb from pancreatic epithelial cell, water follows, opens up CFTR and causes outflow of Cl- to drive antiporter of bicarb

What is the target of somatostatin?

stomach

What are the targets of peptide YY?

stomach and pancreas

Action of CCK:

travels in bloodstream to CCKA receptors, stimulates neural reflex pathways, release of GRP and VIP, causes rise in intracellular Ca2+ leading to vesicle fusion and release of acinar enzymes into duct also stimulates gallbladder contraction -> release of bile causes relaxion of sphincter of Oddi

What are the precursors of proteases?

trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase A and B

Where is gastrin releasing peptide released from?

vagal nerve endings

What two hormones relax the internal anal sphincter?

vasoactive intestinal polypeptide (VIP) and NO


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