GI regulatory substances Flashcards
Where is gastrin secreted from?
G cells in the antrum of the stomach and duodenum
What is the action of gastrin?
Inc gastric H+ secretion, incr growth of gastric mucosa, Inc gastric motility
What stimulates gastrin secretion?
Stomach distention, alkalinization, amino acids, peptides, vagal stimulation
What inhibits gastrin secretion?
pH < 1.5
What is the effect of chronic PPI use on gastrin secretion?
Increases
Where is somatostatin secreted from in the GI system?
D cells of pancreas, GI mucosa
What are the actions of somatostatin in the GI system?
- Decr gastric acid and pepsinogen secretion
- Decr pancreatic and small intestine fluid secretion
- Decr gallbladder contraction
- Decr insulin and glucagon release
- Generally, decreases digestive activity.
What stimulates somatostatin release?
Acid
What inhibits somatostatin release?
Vagal stimulation
What medication is an analogue for somatostatin?
Octreotide
What is the effect of somatostatin on GH release?
Inhibits GH
Where is cholecystokinin released from?
I cells (of the duodenum and jejunum)
What are the effects of CCK?
- Incr GB contraction
- Incr Pancr secretion
- Decr gastric emptying
- Incr sphincter of oddi relaxation
What stimulates CCK release?
Fatty acids, amino acids
What pathways does CCK act on to cause pancreatic secretion?
Neural muscarinic pathways
Where is secretin released from?
S cells of the duodenum
What are the actions of secretin?
- Increase pancreatic bicarb secretion
- Decrease gastric acid secretion
- Increase bile secretion
What stimulates secretin release?
Acid, fatty acids in lumen of duodenum
What is the purpose of HCO3- secretion?
neutralizes gastric acid in duodenum, allowing pancreatic enzymes to function
From where is GIP (glucose-dependent insulinotropic peptide) secreted?
K cells of duodenum, jejunum
What is the exocrine function of GIP?
Decrease gastric H+ secretion
What is the endocrine function of GIP?
Incr insulin release
What stimulates GIP release?
Incr in fatty acids, amino acids, oral glucose
Why are different quantities of insulin released in response to glucose PO vs IV?
GIP is released with PO glucose, but not IV.
Where is motilin released from?
Small intestine M cells (esp duod & jej)
What is the function of motilin?
Produces migrating motor complexes
What are migrating motor complexes?
Peristalsis of the gut that occurs during interdigestive phases, to clear out indigestive substances on for excretion
When is motilin released?
During fasting state
How does erythromycin work to stimulate intestinal peristalsis?
It is a motilin receptor agonist
Were is vasoactive intestinal polypeptide released from?
Parasympathetic ganglia in sphincters, GB, and small intestine
What is the function of VIP?
Incr intestinal water and electrolyte secretion
Incr relaxation of intestinal smooth muscle and sphincters
What stimulates VIP secretion?
Incr by distension and vagal stimulation
What inhibits VIP secretion?
Decr by adrenergic input
What are the symptoms of VIPoma?
islet cell pancreatic tumor that secretes VIP - Watery Diarrhea, Hypokalemia, and Achlorhydria
Loss of what is implicated in achalasia?
NO, causing increased LES tone. (NO increases smooth muscle relaxation)
