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Old 07-21-2014
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Default Q: Pacemaker action potential?

Hello everyone,

According to FA, Phase 4 of pacemaker action potential is called "slow diastolic depolarization" whereas Phase 0 is called "upstroke".
My question is are these "other names" for the phases or just an explanation of what happen during each?

Today while doing UWorld, I stumbled upon this question which I first thought to be "very easy", however due to the descriptions provided by FA for each of the pacemaker phases, I got the question wrong.

UWorld starts by showing a graphical representation of the pacemaker action potential and then asks "Verapamil administration would most likely have which of the following effects on these cells?"

I know that Verapamil, as a calcium channel blocker, would affect Phase 0 of pacemaker action potential as ca influx is responsible for this phase. However, UWorld chooses the answer "Slowed diastolic depolarization". I've to admit that all answers provided are clearly wrong, but the confusion comes from identifying Phase 4 as "diastolic depolarization" not Phase 0, which also occurs during diastole.
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