USMLE class 1 anti arrhythmic

[Blind date18]

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can any one plz help me understand how class 1 anti arrhythmic would increase the threshold potential?

 

[Ven0m]

can any one plz help me understand how class 1 anti arrhythmic would increase the threshold potential?

They act on nodal cells but they don't change the threshold potential (always around -40mV).

The orange line represents depolarization towards the threshold, caused by Na+ influx into the nodal cell (through Na+ channels). Class IA antiarrythmics block some of these Na+ channels, making sodium influx slower. This means the orange line will be less steep and thus take longer to reach -40mV (threshold).

 

[Blind date18]

even i thought the same ,but i have read this in lange flash facts,.Any way thanks mate!!