Harmones Flashcards
Gastrin
Source: G cells of antrum and stomach
Action: increase gastric H+ secretion
increase growth of gastric mucosa
Increase gastric motility
Regulation: increased by stomach distenstion/alkalinization, amino acids, peptides, vagal stimulation
Decreased by stomach ph
Motilin
Source: small intestine
Action: produces migrating motor complex
Regulation: increases in fasting state
Motilin receptor agonists (erythromycin) stimulate intestinal peristalsis
GIP
Source: K cells of duodenum and jejunum
Action:
Exocrine: decrease gastric H+ secretion
Endocrine: increase insulin release
Regulation: increased by fatty acids, amino acids, oral glucose
Secretin
Source: S cells of duodenum
Action: increase pancreatic HCO3- secretion
Decrease gastric acid secretion
Increase bile secretion
Regulation: increased by acid, HCl most potent, fatty acids in lumen of duodenum
Begins at pH
Somatostatin
Source: D cells of pancreatic islets and GI mucosa
Action: decreased gastric acid and pepsinogen secretion
decreased pancreatic and small intestine fluid secretion
decreased gallbladder contraction
decreased insulin and glucagon, CCK and gastrin release
Regulation: increased by acid, decreased by vagal stimulation
antigrowth hormone effects
Nitric Oxide
Action: increased smooth muscle relaxation including lower esophageal sphincter
Loss is implicated in increased LES tone of achalasia
VIP
Source: parasympathetic ganglia in sphincters, gallbladder, small intestine, pancreatic islet cells
Action: increased intestinal water and electrolyte secretion
Increased relaxation of intestinal smooth muscle and sphincters
Inhibits gastric H+ secretion and stimulates pancreatic bicarbonate and Cl-
Regulation:
increased by distenstion and vagal stimulation
Decreased by adrenergic input
VIPoma: watery diarrhea, hypokalemia, and achlorhydria-inhibited by somatostatin
Intrinsic factor
Source: parietal cells of stomach
Action: viamin B12 binding protein required for B12 uptake in terminal ileum
Gastric Acid
Source: parietal cells of stomach (upper glandular layer)
Action: decrease stomach pH by secreting HCl
Regulation: increased by histamine (cAMP), ACh (Ca2+), gastrin (Ca2+) gastrin is trophic leading to hyperplasia
Decreased by somatostatin, GIP, prostaglandin, secretin
Gastrinoma: located in pancreas
gastrin secreting tumor that causes high level of acid secretion and ulcers refractory to medical therapy
Diarrhea and abdominal pain (MEN type 1)
Pepsin
Source: chief cells (stomach)
Action: protein digestion
Regulation: increased by vagal stimulation, local acid
pepsinogen activated to pepsin by H+
HCO3-
Source: mucosal cells (stomach, duodenum, salivary glands, pancreas) Brunner glands (duodenum)
Action: neutralizes acid
regulation: increased by pancreatic and biliary secretion with secretin
HCO3- trapped in mucus that covers the gastric epithelium
CCK
Source: I cells of duodenum and Jejunum
Action: increase pancreatic secretion
Increase gallbladder contraction
Decrease gastric emptying
Increase sphincter of Oddi relaxation
Regulation: increased by fatty acids and amino acids
Acts on muscarinic pathways to cause pancreatic secretion
a-amylase
Starch digestion
Secreted in active form from pancrease
Lipase, phospholiase A, colipase
Secreted from pancreas
Fat digestion
Proteases
Secreted from pancreas
Include trypsin, chymotrypsin, elastase, carboxypeptidases
Secreted as zymogens
