Gastrointestinal Regulatory Substances Flashcards
What is the source, action, and regulation of gastrin secretion?
Source: G cells (antrum of stomach, duodenum)
Action: increase gastric H+secretion, increase, growth of gastric mucosa, increase gastric motility
Regulation: increased by stomach distention/ alkalinization, amino acids, peptides, vagal stimulation via gastrin-releasing peptide (GRP), decreased by pH < 1.5, increased by chronic PPI use.
Significantly increased in Zollinger-Ellison syndrome (gastrinoma)
What is the source, action, and regulation of somatostatin secretion?
Source: D cells (pancreatic islets, GI mucosa)
Action: (DECREASE EVERYTHING) decrease gastric acid and pepsinogen secretion, decrease pancreatic and small intestine fluid secretion, decrease gallbladder contraction, decrease insulin and glucagon release
Regulation: increased by acid, decreased by vagal stimulation
Notes: Inhibits secretion of various hormones (encourages somato-stasis). Octreotide is an analog used to treat acromegaly, carcinoid syndrome, and variceal bleeding
What is the source, action, and regulation of cholecystokinin secretion?
Source: I cells (duodenum, jejunum)
Action: increase pancreatic secretion, increase gallbladder contraction, delay gastric emptying, promote sphincter of Oddi relaxation
Regulation: increased by fatty acids, amino acids
Acts on neural muscarinic pathways to cause pancreatic secretion
What is the source, action, and regulation of secretin secretion?
Source: S cells (duodenum)
Action: increase pancreatic HCO3–secretion, decrease gastric acid secretion, increase bile secretion
Regulation: increased by acid, fatty acids in lumen of duodenum
Notes: HCO3–neutralizes gastric acid in duodenum, allowing pancreatic enzymes to function.
What is the source, action, and regulation of GIP (gastrin inhibitory peptide) secretion?
Source: K cells (duodenum, jejunum)
Action:
- Exocrine: decrease gastric H+secretion
- Endocrine: increase insulin release
Regulation: increased by fatty acids, amino acids, oral glucose
Oral glucose load leads to increased insulin compared to IV equivalent due to GIP secretion.
What is the source, action, and regulation of motilin secretion?
Source: Small intestine
Action: Produces migrating motor complexes (MMCs)
Regulation: increased in fasting state
Notes: Motilin receptor agonists (eg, erythromycin) are used to stimulate intestinal peristalsis.
What is the source, action, and regulation of vasoactive intestinal poypeptide secretion?
Source: Parasympathetic ganglia in sphincters, gallbladder, small intestine
Action: increase intestinal water and electrolyte secretion, increase relaxation of intestinal smooth muscle and sphincters
Regulation: increased by distention and vagal stimulation, decreased by adrenergic input
Notes: VIPoma—non-α, non-ßislet cell pancreatic tumor that secretes VIP. Watery Diarrhea, Hypokalemia, and Achlorhydria (WDHAsyndrome).
