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q23 - lisa773
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05-08-2005, 08:57 AM
On internal medicine rounds, the attending is reviewing the myocardial action potential. In which of the following phases of the action potential do the voltage-gated potassium channels begin to open?
A. Phase 0 B. Phase 1 C. Phase 2 D. Phase 3 E. Phase 4
05-08-2005, 10:55 AM
in myocardial action potential
phase 0= inward na influx. na channel open. phas1====na channel start closing and potassium chanel start open (K pump outward)(Phae 0 end and platuse start) phase2.......inward ca influx ........ca channel open.(platuae) phase3...K channel completely open(repolarization). phase4....resting stage.
05-08-2005, 02:50 PM
voltage gated potassium channels open during later part of phase 2
05-08-2005, 02:57 PM
I think they open in phase 3 because that's how repolarization occurs. And att, I believe that the overshoot that occurs after phase 0, phase 1, is due to the nongated potassium channels. The voltage gated ones open until repolarization, phase 3. Please, anybody more comments to make this clear.
05-08-2005, 11:46 PM
is the phase 1 overshoot due to K or chloride?? i think it is controversial . if it is K then the answer has to be phase 1 right ?
05-09-2005, 06:03 AM
in kaplan they say that K efflux does occur in phase 1 causing the slight depolarisation but they didn't specify that it's thru the voltage gated, so phase 2(latter part) should be a safe answer.
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