GI physiology lecture 4

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gastric motility
- filling: involves receptive relaxation, triggered by eating, mediated by vagus nerves
- storage: in body of stomach
- mixing: in antrum of stomach
- emptying: regulated by cells in duodenum
pce makers of the gut
- interstitial cells of cajal
- conducts slow wave to smooth muscle
- L type Ca action potential (allows in Ca)
force of muscle contratcion
- directly related to amplitude and frequency of APs
- AP occurs once slow wave reaches AP thresh hold
Antral contraction
- propulsion: bolus pushed toward pyloris
- Grinding: the antrum churns trapped material
- Retro pulsion: bolus pushed back into proximal stomach
Gastric emptying:
- stomache
- amount of chyme regulates strength of contraction
- duodenum
- fat: sdf
- Acid: inhibbits emptying until neutralized
- Hypertonicity: inhibitted when osmolarity starts to rise
- distention: too much chyme in the duodenum inhibits emptying of more chyme
- factors outside the GI system
- emotion: alters autonomic system which can inhibit or stimulate emptying
- Pain: increases symp activity which inhibits motility and emptying
vomiting/emisis
- coordinated by vommiting center in medulla from brain stem
- diaphragm pushes down on stomache
- abdominal viscera contractsvorcing viscera up
- therefor stomache squeezed
vomitin/emisis
- les and ues contract
- glotiss closes and uvula is raised to close off nose
- initiated ba tactile stimulation at back of throat and irriatation of stomach
- chemicals (emitics)trigger zone next to vomiting center
- psychogenic factors can effect too
pancrease
- both exoctrine and endocrine tissue
- located behind and below stomach
- endocrine: islets of langerhans secret insulin and glucagon
- exocrine: 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:
- chymostrypsinogen
- procarboxypeptidase
- procolipase
- prophospholipase
- enzymes:
- chymotrypsin
- carboxypeptidase
- colipase
- phospholipase
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 calcium
- both trigger phosphorylation of structural and regulatoryproteins
- enzymes are then washed into duodenum by ductalar secretion
secretin

stimulates CFTR by cAMP
negative feed back by secretin
- increased secretin release
- increase in ductalar bicarbinate secretion
- lowerse ph in duodenum
- s cells release more
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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?

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GI physiology lecture 4

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2011-03-01T17:22:21Z

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