GI-Physiology Flashcards
(50 cards)
What is the source of gastrin?
G cells located in the antrum of the stomach and the duodenum
What does gastrin do?
increase gastric acid secretion, and promote growth of gastric mucosa and gastric motility
What things promote gastrin production/release? Inhibit?
Promote- stomach distension, AAs from protein directly, vagal stimulation via Ach, food (food has buffering capacity leading to alkalization)
Inhibits- pH below 2
What things lead to increased gastrin levels?
- chronic atrophic gastritis (e.g. H. pylori)
- Zollinger-Ellison syndrome
- chronic PPI use
Where is somatostatin made?
D cells in the stomach antrum, pancreas and the GI mucosa
What does somatostatin do?
decrease gastric acid secretion and pepsinogen secretion from chief cells
decrease insulin, GH, and glucagon release
decrease pancreatic and small intestine fluid secretion
decrease gallbladder contraction
What stimulates somatostatin release? Inhibits?
Promote- acid
Inhibits- vagal stimulaton via Ach
Where is Cholcystokinin made?
I cells in the duodenum and jejunum
What does cholecystokinin do?
increase pancreatic secretions and gallbaldder contraction
decreases gastric emptying
relaxes the sphincter of Oddi
What causes cholecystokinin release?
fatty acids and AAs
Where is secretin produced?
S cells in the duodenum
What does secretin do?
increase pancreatic HCO3- and bile secretion
decrease gastric acid secretion
What promotes secretin release?
acid and fatty acids in the lumen of the duodenum (the HCO3- produced neutralizes gastric acid in the duodenum to allow pancreatic enzymes to function)
Where is Glucose-dependent insulinotropic peptide (GIP)(aka gastric inhibitory peptide) made?
K cells in the duodenum and jejenum
What does GIP do?
exocrine: decrease gastric H+ secretion
endocrine: increase insulin release
What promotes GIP release?
fatty acids, AAs, and oral glucose (thus oral glucose leads to more insulin release via GIP influence than IV)
Where is motilin made?
M cells in the small intestine
What does motilin do?
The main function of motilin is to increase the migrating myoelectric complex (MMCs) component of gastrointestinal motility and stimulate the production of pepsin. Motilin is also called “housekeeper of the gut” because it improves peristalsis in the small intestine and clears out the gut to prepare for the next meal.
A high level of motilin secreted between meals into the blood stimulates the contraction of the fundus and antrum and accelerates gastric emptying. It then contracts the gallbladder and increases the squeeze pressure of the lower esophageal sphincter. Other functions of motilin include increasing the release of pancreatic polypeptide and somatostatin
What are some motilin receptor agonists?
Erythromycin and related antibiotics act as non-peptide motilin agonists, and are sometimes used for their ability to stimulate gastrointestinal motility.
Where is vasoactive intestinal polypeptide (VIP) made?
parasympathetic ganglia in sphincters, gallbladder, and small intestine
What does VIP do?
With respect to the digestive system, VIP seems to induce smooth muscle relaxation (lower esophageal sphincter, stomach, gallbladder), stimulate secretion of water into pancreatic juice and bile, and inhibit gastric acid secretion and absorption from the intestinal lumen.
Its role in the intestine is to greatly stimulate secretion of water and electrolytes, as well as relaxation of enteric smooth muscle, dilating peripheral blood vessels, stimulating pancreatic bicarbonate secretion, and inhibiting gastrin-stimulated gastric acid secretion. These effects work together to increase motility.
It also has the function of stimulating pepsinogen secretion by chief cells
What are the symptoms of excess VIP production, as in the case of a VIPoma in the pancreas?
Copius Watery Diarrhea
Hypokalemia
Achlorhydria
(WDHA syndrome)
Where is intrinsic factor made?
parietal cells of the stomach
What does intrinsic factor do?
it is required for vitB12 uptake in the terminal ileum
