GI Regulatory Substances Flashcards
Gastrin
From G cells in stomach and duodenum
inc H+ secretion by dir parietal cell stimulation and inc histamine from ECLs
Vagal stim –> GRP –> stimulates gastrin
Also act by distention and nutrients in stomach
Somatostatin
D cells (pancreas and GI mucosa)
dec gastric acid and pepsinogen, dec pancreatic and SI fluid secretion, dec gallbladder contraction, dec insulin and glucagon release
Act by acid and inactivated by vagal
CCK
I cells (duodenum and jejunem)
inc pancreatic secretion, gallbladder contraction and sphincter of Oddi relaxation + less gastric emptying
Acts thru neurons (muscarinic) –> pancreas
Secretin
S cells (duodenum)
Inc pancreatic bicarb secretion, inc bile secretion and dec gastric acid secretion
Act by acid or FAs in lumen
GIP
K cells (duodenum and jejunem)
Dec gastric H+ and in insulin release
Act by FAs, AAs and ORAL glucose
Motilin
SI
Prod migrating motor complexes
Inc in fasting state
Agonists - like erythromycin for motility
VIP
Parasymp ganglia in sphincters, gallbladder and SI
Inc intestinal water and electrolyte secretion + relaxation of smooth muscle and sphincters
Act by distention and inact by adrenergic
VIPomas cause diarrhea, hypokalemia and achlorhydria
NO
Inc smooth muscle relaxation esp at LES
Ghrelin
Stomach
Inc appetite when fasting
Inc in Prader-Willi
Intrinsic Factor
Parietal Cells (stomach)
Vit B12 binding protein for uptake in terminal ileum
Gastric Acid
Parietal Cells (stomach)
Act by histamine, Ach and gastrin
Inact bu prostaglandins, somatostatin, GIP and secretin
Pepsin
Chief Cells (stomach)
Protein digestion
Inc by vagal stimulation and local acid
Pepsinogen –> pepsin (active) via H+
Bicarbonate
Mucosal cells (stomach, duodenum, salivary glands, pancreas and Brunner glands)
Neutralizes acid
