pharm-na channel blockers

[HiddenTruth]

alrite, so i dont get it.
1. by what mechanism of action do na channel blockers increase threshold potential? and

2. how do potassium channel blockers increase effective refr period by prolonging the action potential duration (is it all dependent on time--then it makes sense. But in the k channel blocker graph, it is a horizantal increase (increase APD) which results in increase in ERP and in the na channel blocker graph, the ERP is increased by a vertical increase in the ERP w a drug. Please advise. Thanks

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[DrBuzzLightYear]

think about the role that each ion plays in either initiating or terminating the depolarization and the direction in which it moves. if you ****** an ion's movement with a channel blocker, then you'll prolong the preceding stage.