What are the functions of gastrin?
Gastrin increases acid secretion, promotes growth of the gastric mucosa, and increases gastric motility
What are stimuli for the release of gastrin?
Distension, amino acids, vagal stimulation
What serves as negative feedback for gastrin release?
Acid secretion; a pH < 1.5 will inhibit gastrin secretion
A patient presents with peptic ulcer disease refractory to medical treatment. On endoscopy, he is found to have multiple ulcers in the stomach and a few in the jejunum. Fasting gastrin levels are markedly elevated. What is the likely diagnosis?
Zollinger-Ellison syndrome due to ectopic production of gastrin
What two amino acids are especially potent stimulators of gastrin release?
Tryptophan and phenylalanine
Which cells in the gastrointestinal tract make cholecystokinin?
I cells of the duodenum and jejunum
What are the actions of cholecystokinin?
Stimulation of gallbladder contraction and pancreatic enzyme secretion; slowing of gastric emptying
What stimulates cholecystokinin release?
The presence of fatty acids and amino acids in the duodenum
In cholelithiasis, pain worsens after the ingestion of what type of foods?
Fatty foods; due to stimulation of cholecystokinin release, which causes gallbladder contraction
Secretin is produced by which cells?
S cells of the duodenum
What are the actions of secretin?
Increases bicarbonate secretion, increases bile acid secretion, decreases gastric acid secretion
Which two substances stimulate secretin release within the duodenum?
Acid and fatty acids
Secretin-stimulated pancreatic bicarbonate functions to neutralize _____ _____ within the _____.
Gastric acid; duodenum
Why is it important that secretin-stimulated bicarbonate neutralize gastric acid within the duodenum?
Pancreatic enzymes would otherwise be denatured and nonfunctional in the acidic environment created by unopposed gastric acid
Somatostatin is made by which cells?
D cells of pancreatic islets and gastrointestinal mucosa
Does somatostatin lead to increased or decreased pepsinogen secretion? Increased or decreased gastric acid secretion?
Does somatostatin increase or decrease pancreatic secretions?
Does somatostatin increase or decrease fluid secretions in the small intestine?
What effect does somatostatin have on the gallbladder?
Somatostatin decreases gallbladder contraction
The presence of what substance in the gut lumen causes increased somatostatin release?
What functions to inhibit somatostatin release?
Given the functions of somatostatin, why is it classified as an antigrowth hormone?
Somatostatin inhibits digestion and absorption of nutrient, thereby preventing the body from receiving nutrient needed for growth
What are two tumors that can be treated with somatostatin?
Vasoactive intestinal peptide tumors and carcinoid tumors; somatostatin reduces symptoms by inhibiting secretions from the tumors
Glucose-dependent insulinotropic peptide is made by which cells?
K cells of the duodenum and jejunum
What is the exocrine regulatory effect of glucose-dependent insulinotropic peptide?
Decreased secretion of gastric acid
What is the endocrine regulatory effect of glucose-dependent insulinotropic peptide?
Increased release of insulin
What increases glucose-dependent insulinotropic peptide secretion?
Fatty acids, amino acids, and oral glucose load
Why is an oral glucose load used more rapidly by the body than an equivalent load that is given intravenously?
Because oral (but not intravenous) glucose stimulates glucose-dependent insulinotropic peptide, which stimulates insulin release
Where is vasoactive intestinal polypeptide secreted within the gastrointestinal tract?
Parasympathetic ganglia in sphincters, gallbladder, small intestine
Vasoactive intestinal polypeptide _____ (increases/decreases) intestinal water and electrolyte secretion.