Action Potential

[Elias Jeryes]

Hello everyone,

I'm a medicine student and i have final exam in general physiology, one of the topics in the course is Action Potential,

I can say i understand the action potential pretty well, but I have something to ask about which i still don't know.

As action potential develops from supratheshold local depolarization, sodium influx depolarizes the membrane until the inactivation gate of the voltage-gated sodium channel is closed at the peak of the diagram, and so on the membrane at this stage can't be depolarized again until the voltage-gated sodium channel retains its original configuration in which the activation gate is closed and the inactivation gate is opened, well, my question is : when does the voltage-gated sodium channel retains its original ( or resting) configuration after the peak on the diagram ?

and thank you for your cooperation

Edited June 2, 2016 by Elias Jeryes

[Function]

Have you heard of relative refractory period and absolute refractory period? Might want to look this up first.

The absolute refractory period (ARP) is the period in which all of the Na-channels are still inactivated. Your cell is busy repolarizing (actually hyperpolarizing). The more it gets hyperpolarized, the more the h-gates open up again and your inactivation is being undone. This is your relative refractory period: it is possible, if you get a strong enough stimulus, to reactivate Na-channels because their h-gate starts opening.

 

(look up m-gates and h-gates of the Na-channels and the equivalent n-gate of K-channels; note that the h-gate is specific for INactivation of the Na-channel: an open m-gate = activated Na-channel; a closed m-gate = deactivated; a closed h-gate = inactivated; note also that K-channels can, because of this strict terminology, only be activated/deactivated, not inactivated: they only have 1 functional gate)

[Elias Jeryes]

thank you Professor S. Laureys for your reply, and yes I know about absolute refractory period ( in which any stimulus no matter how strong it is, it won't cause an action potential) and the relative refractory period ( in which depolarizing is possible but only with a stronger stimulus) and thank you for your help :)

[Function]

Oh god no please, I am not prof. Steven Laureys (I'm nowhere near a professor, actually: I'm still a medicine student) I only quote him in my signature

Edited June 2, 2016 by Function