GI Hormones Flashcards
Explain G cells
G cells are present in (decreasing order) –> antrum, duodenum, and jejunum
activated by vagus/ENS (GRP), distention, and amino acids
inhibited by acids (<1.5 pH), somatostatin, and secretin
G cells will release gastrin which increase HCl release, pepsinogen (which HCl can convert to pepsin to break down proteins), and slight increase in gastric motility, and MUCOSAL GROWTH
Zollinger-Ellison syndrome (gastrinoma), chronic PPI use (increase gastrin), atrophic gastritis (increase gastrin), pentagastrin (synthetic form of gastrin)
Explain I cells
I cells are present in –> duodenum, jejunum, and ileum
activated by FA, AA, and acid*
I cells release CCK which inhibits gastric emptying (decreasing hunger by keeping food in stomach longer), CCK increases bile secretion (due to contraction of gallbladder and relaxation of sphincter of oddi), pancreatic enzymes and bicarb secretions, and growth of exocrine pancreas
worsens pain of cholelithiasis due to contraction of gallbladder against blocked cystic duct
Explain S cells
S cells present in –> duodenum, jejunum, ileum
activated by acid (<4.5 pH) and FA*
S cells release secretin which inhibits gastrin and gastric HCl BUT increases pancreatic and biliary bicarb secretion, pepsinogen, and growth of exocrine pancreas
bicard neutralizes gastric acid in duodenum preventing duodenal ulcers, CF px have diminished response to secretin because their CFTR is defective, can’t exchange bicarb –> want to decrease Cl and give them dietary enzyme supplements
Explain K cells
K cells present in –> duodenum and jejunum
activated by FA, AA, and carbs*
K cells release GIP which inhibits gastric HCl and is inhibited by DPP-4
GIP increase insulin release so for px with type 2 diabetes, want to give them GIPR agonists and DPP-4 inhibitors
Where are G cells?
pylorus (mainly), duodenum, and jejunum
What are G cells activated or inhibited by?
activated by vagus/ENS (GRP), distention, and AA
inhibited by acid (<1.5 pH), somatostatin, and secretin
What do G cells release?
G cells release gastrin which increase HCl secretion, pepsinogen, and slight increase in gastric motility, and MUCOSAL GROWTH
Where are I cells?
duodenum, jejunum, ileum
What are I cells activated or inhibited by?
activated by FA, AA, acid*
What do I cells release?
I cells release CCK which inhibit gastric emptying and increase release of bile (contraction of gallbladder and relaxation of sphincter of oddi), pancreatic enzyme and and bicarb, and growth of exocrine pancreas
Where are S cells?
duodenum, jejunum, and ileum
What are S cells activated or inhibited by?
activated by acid (<1.5 pH) and FA*
What do S cells release?
S cells release secretin which inhibits gastrin and gastric HCl
increase pancreatic and biliary bicarb secretion, pepsinogen, and growth of exocrine pancreas
Where are K cells?
duodenum and jejunum
What are K cells activated or inhibited by?
activated by FA, AA, and carbs*
What do K cells release?
K cells release GIP which is inhibited by DPP-4 and inhibits gastric HCl
GIP increases insulin release
Explain L cells
L cells present (increasing order) in –> duodenum, jejunum, ileum, colon
activated by carbs, FA, and AA*
L cells release GLP-1 which inhibits gastric emptying and is inhibited by DPP-4
GLP-1 increases insulin release so want to use GLP-1 receptor agonist and DPP-4 inhibitor in px with type 2 diabetes
Where are L cells?
duodenum, jejunum, ileum, and colon
What are L cells activated or inhibited by?
carbs, FA, and AA*
What do L cells release?
L cells release GLP-1 which is inhibited by DPP-4 and inhibits gastric emptying
increase insulin release
Explain M cells
M cells present in –> duodenum and jejunum
activated by fasting, acid, and fat
M cells release motilin which is inhibited by feeding
Motilin activates migrating motor complex (MMC) –> increase gastric and SI motility while fasted (causes borborygmi which is growling), necessary to remove undigested food and prevent bacterial growth
Where are M cells?
duodenum and jejunum
What are M cells activated or inhibited by?
activated by fasting, acid, fat
What do M cells release?
M cells release motilin which is inhibited by feeding
increases migrating motor complex (activates gastric and SI motility while fasted to remove remaining undigested food and prevent bacterial growth)
