GI physiology lecture 4


gastric motility


filling: involves receptive relaxation, triggered by eating, mediated by vagus nervesstorage: in body of stomachmixing: in antrum of stomachemptying: regulated by cells in duodenum


pce makers of the gut


interstitial cells of cajalconducts slow wave to smooth muscle L type Ca action potential (allows in Ca)


force of muscle contratcion


directly related to amplitude and frequency of APsAP occurs once slow wave reaches AP thresh hold


Antral contraction


propulsion: bolus pushed toward pylorisGrinding: the antrum churns trapped materialRetro pulsion: bolus pushed back into proximal stomach


Gastric emptying:


stomacheamount of chyme regulates strength of contractionduodenum fat: sdfAcid: inhibbits emptying until neutralizedHypertonicity: inhibitted when osmolarity starts to risedistention: too much chyme in the duodenum inhibits emptying of more chymefactors outside the GI systememotion: alters autonomic system which can inhibit or stimulate emptyingPain: increases symp activity which inhibits motility and emptying


vomiting/emisis


coordinated by vommiting center in medulla from brain stemdiaphragm pushes down on stomacheabdominal viscera contractsvorcing viscera uptherefor stomache squeezed


vomitin/emisis


les and ues contractglotiss closes and uvula is raised to close off noseinitiated ba tactile stimulation at back of throat and irriatation of stomachchemicals (emitics)trigger zone next to vomiting centerpsychogenic factors can effect too


pancrease


both exoctrine and endocrine tissuelocated behind and below stomachendocrine: islets of langerhans secret insulin and glucagonexocrine: secretes pancreatic juice with enxymes from acinar cellsand aqueous alkaline from duct cells


pancreatice enzymes:


pancreatic secretions


trypsunogen: activated by enteropeptidase into trypsin which converts zymogens into enzymes


zymogens and enzymes


zymogens: chymostrypsinogenprocarboxypeptidaseprocolipaseprophospholipase
enzymes:chymotrypsincarboxypeptidasecolipasephospholipase


comthin


trypsin out put


occurs only during feeding times and is greatly reduced at night during fasting


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secretin: creates cAMP CCK (colocystic kinin): mobilizes intracellular calciumboth trigger phosphorylation of structural and regulatoryproteinsenzymes are then washed into duodenum by ductalar secretion


secretin


stimulates CFTR by cAMP


negative feed back by secretin


increased secretin releaseincrease in ductalar bicarbinate secretionlowerse ph in duodenums cells release more


sadklhj


hormonal control of pancreatic secretion


type up system looop


what is the evidence that amino acids stimulate CCK secretion from I cells in the duodemun?