Reg. GI Fxn Flashcards
Five Functions of the gut
motility secretion digestion absorption storage
Paracrine definition
peptides secreted from cells with subsequent diffusion through the interstitial space to contact and affect other cells
Autocrine definition
secretions of a given cell modify or regulate functions of the same cell
Neurocrine definition
secretion by enteric neurons of neuromodulators or regulatory peptides that affect nearby muscle cells, glands, or blood vessels.
Secretin: production site
duodenum and upper jejunum; S cells
Secretin: Action
stimulates HCO3- secretion and inhibits acid secretion (nature’s anti-acid). Stimulates exocrine pancreatic and biliary secretions of water, bicarb. gastric mucus and pepsinogen; endocrine pancreatic secretions of insulin, glucagon, and somatostatin; and pancreatic growth
Inhibits gastric acid secretion, motility of intestine and gastric mucosal growth.
Secretin: Release stimulus
Gastric acid, fat, protein, bile acids, and herbal extracts
Controlled by action of hormones: CCK, hormonal-neuronal control (CCK-vagal)
Gastrin: prod. site
stomach (pylorus and antrum) and duodenum G cells
Gastrin: Action
Stimulates acid secretion and growth of stomach epithelium (cancer marker)
Gastrin: Release stimulus
Protein, increased high gastric acidity, gastric distention
Cholecystokinin: Production site
Duodenum, jejunum, ileum; endocrine I (“i”) cells and enteric neurons of duodenum and jejunum
Cholecystokinin: Action
Stimulates pancreatic enzyme secretion and gallbladder contractions; inhibits food intake and gastric emptying
Cholecystokinin: Release stimulus
Fats and protein
Gastric inhibitory polypeptide: Production site
duodenum and jejunum
Gastric inhibitory polypeptide: action
inhibits gastric secretions and emptying and stimulates insulin secretion. Slows movement of ingesta particularly from stomach to intestine.
Gastric inhibitory polypeptide: release stimulus
fat and glucose (glu. in duodenum)
Motilin: Production site
M cells of duodenum and jejunum (jejunum lesser extent than duod.)
Motilin: Action
induction/regulation of phase III of the MMC (migrating motor complex) during fasting (digestive state). Works on both muscles and nerves. Stimulates gastric emptying between meals and secretion of pepsinogen (protein digesting enzyme)
Motilin: Release stimulus
Acetylcholine
Cholinergic neurons are typically _________ to gut? inhibit or stim? Molecule?
stimulatory, Acetycholine
adrenergic neurons are typically __________ to gut? inhibit or stimulatory? Molecule?
Inhibitory: adrenaline/epinephrine
Gastrin forms
G-17 (90%) and G-34 (10%, duodenum)
Gastrin binds to ____________
CCK-2 receptor, g-protein coupled receptor. Causes stimulation of gastric acid secretion and hyperplasia of enterochromaffin-like cells.
Gastrin & histamine =?
Gastrin increases acid secretion indirectly by stimulation of histamine release from ECL which can activate H2 receptors on acid secreting gastric parietal cells.
CCK receptors and locations
CCK-1 alimentary, CCK-2 brain
Aldosterone: definition
steroid hormone (mineralocorticoid) secreted by outer zone glomerulosa of adrenal cortex after low-salt diet, angiotensin, adrenocorticotropic hormone, or high potassium levels.
Aldosterone: function
act on distal convoluted tubules and collecting ducts of the kidney causing secretion of K+ and reabsorption of Na+ and H2O.
Aldosterone: GI fxn.
stimulates sodium and water reabsorption from the gut and salivary glands in exchange with K+ ions. Species dependent: water and Na+ reabsorption in proximal colon and decrease absorption in distal colon.