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Test 2 Questions and Answers

Test 2 Questions and Answers - Term test 2 questions and...

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Term test 2 questions and answers 1. Describe the processes involved in secreting bicarbonate ion from exocrine pancreatic duct cells. Describe specifically how duct cell bicarbonate secretion is altered by hormonal secretions in the inhibitory intestinal phase of gastric secretion? Pancreatic duct cell lumen ISS K+ H+ ATP Cl- HCO 3 - Cl- 3Na+ 2K+ ATP CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - CA K+ metabolism H+ Na+ H 2 O + CO 2 H 2 CO 3 HCO 3 - + The inhibitory phase of gastric secretion promotes the release of secretin from S cells and CCK from I cells. Secretin and CCK control HCO3- production and release by: number of H + -K + ATPase to increase removal of H + to maintain HCO 3 - production. cAMP secretin secretin Rm # and open time of Cl - channels to increase Cl - gradient to increase HCO 3 - movement activates K+ channels to hyperpolarize cell to increase Cl - out and therefore lots of lumenal Cl- for HCO 3 - movement out. CCK gastrin/CCK Rc Ca ++
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2. Describe the changes in membrane potential, ion movement and membrane channels responsible in the development of slow waves and action potentials (spike potentials) in intestinal smooth muscle. Generally, to open a closed sphincter, stimuli proximal to the sphincter will cause relaxation, and stimuli distal to the sphincter will cause constriction, describe how this might happen. Slow waves: Depolarization via voltage gated Ca++ channels 1. Open – Ca++ flux into cell 2. Inactive – no Ca++ flux 3. Closed – no Ca++ flux Repolarization via Ca++ dependant K+ channels 2. Open – K+ flux out of cell 3. Closed – no K+ flux 1 2 3 Spike potentials: 4. Reach threshhold (-40mV) Depolarization via voltage gated Ca++ channels 4. Open – Ca++ flux into cell 5. Inactive – no Ca++ flux 6. Closed – no Ca++ flux Repolarization via: a) Ca++ dependant K+ channels 5. Open – K+ flux out of cell 7. Closed – no K+ flux b) Ca++ dependant K+ channels 5. Open – K+ flux out of cell
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