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GI Phys Stomach

USCSOM Physiology: GI Lecture Part III - Stomach

QuestionAnswer
Migrating motility complex periodic wave of contractions every 90 minutes
What is MMC stimulated by? motilin
What inhibits motilin production? eating
What antiobiotic is a motilin receptor agonist? erythromycin
What is dumping syndrome? Common cause? Tx? rapid gastric emptying, gastrectomy, smaller more frequent meals
What is gastroparesis? Common cause? Tx? delayed gastric emptying, chronic diabetes, muscarinic agonists and more frequent smaller meals
What are four gastric secretions? HCl, mucus, Intrinsic Factor, Pepsinogen
HCl gastric secretion function? secreted by parietal/oxyntic, activates pepsinogen, kills bacteria, breaks down connective tissue
What is function of Intrinsic factor? binds Vit B12
What happens if there is no intrinsic factor secreted? pernicious anemia
What is the function of pepsinogen? a protease that is converted to pepsin by acid
Describe Oxyntic glands. Parietal Cells for HCl and intrinsic factor, Chief cells for pepsinogen, Mucus cells
Describe pyloric glands. G-cell for gastrin and mucus cells
How much HCl is secreted daily? 1-2L
Severe vomiting causes loss of what two ions? H+ and K+
What types of mechanisms are involved in HCl production? carbonic anhydrase, H/K ATPase, Bicarb/Cl exchanger
What are the three acid secreting stimulants? Histamine, gastrin, ACh
What is the strongest stimulant of acid secretion? Histamine
What stimulates histamine release in GI acid secretion? gastrin and ACh
What drug blocks H/K ATPase? omeprazole
What drugs block H2 histamine receptors? cimetidine and ranitidine (Zantac)
Is histamine a paracrine or endocrine hormone? paracrine
Is gastrin a paracrine or endocrine hormone? endocrine
What kind of glands secrete gastrin? pyloric glands
What type of drug blocks muscarinic ACh recpetors? atropine
What nerve stimulates ACh release? Vagus
What two things stimulate gastrin release? gastrin releasing peptide (GRP); peptides/AA
What inhibits gastrin release? somatostatin
What stimulates somatostatin release? acid, low stomach pH
What inhibits somatostatin release? ACh
What are the basal secretions of somatostatin and gastrin? high somatostatin, low gastrin, bc there is a low pH
What are the 3 phases of stimulated secretion? Cephalic Phase, Gastric Phase, Intestinal Phase
What stimulates the cephalic phase? thoughts of food, conditioned reflexes, tasting/smelling food
What is released during the cephalic phase? GRP (bombesin) and ACh
What is the gastric phase? when food enters the stomach
What are the three major components of the gastric phase? pH, distension, peptides/amino acids
What is the intestinal phase? when food enters the small intestine
What two things stimulate acid release in the intestinal phase? enterooxyntin
What does enterooxyntin do? in response to what? increase acid release in response to distension of small intestine
What hormones contribute to ending acid secretion? secretin, gastic inhibitory peptide, GIP
What is GIP? What does it inhibit? What does it release? What is it produced by? What is it stimulated by? glucose-dependent insulinotropic peptide; inhibits gastrin/acid, increases insulin, produced by endocrine cells, stimulated by products of digestion
What is mucus secretion inhibited by? alpha-adrenergic agonsts; stress may cause ulcers
What are two common causes for stomach ulcers? Helicobacter pylori and NSAIDs
How do you test for presence of H. Pylori? Urea breath test for urease enzyme
What is GERD? Gastroesophageal Reflux Disease
What are some Txs for GERD? lifestyle changes, antacids, pro-motility drugs
What are the 3 steps of vomiting? nausea, retching, vomiting
Where in the brainstem is the 'vomiting center' located? medulla
What things stimulated the vomiting center? vestibular stimulation, GI chemoreceptors, visceral afferents, psychic stimuli (odors/fears)
What types of drugs would work as anti-emetics? muscarinic ACh receptor antagonists and dopamine receptor antagonsists
What are the two openings to and from the stomach? LES and pyloric sphincter
What are the upper and lower stomach named? Orad (upper) and Caudal (lower)
Describe the orad stomach. weak mm, tonically contracted, oxyntic glands
Describe the caudal stomach. strong mm, phasic contraction, pyloric glands
Describe the intrinsic contractile activity of the stomach. Interstitial cells of Cajal, slow waves, BER
CCK is released in response to what? fat
Secretin is released in response to what? acid
Gastric inhibitory peptide is released in response to what? food
Created by: jlellerm