Refractory Period

maldonado pedro at mulab.physiol.upenn.edu
Tue Apr 21 16:31:07 EST 1992


>On 04-17-92 ALLEN SMITH wrote:
>        There seems to be a contradiction in the definitions of refractory
>period and repolarization time. What's the name for how long it takes
>before a neuron can send a signal again?

	There seems to be a confusion about the refractory period.
Actually, there are TWO refractory periods. One Absolute refractory
period in which the Na channels are inactive and no matter how much
current is passed through the membrane, no action potential can be
triggered. The Relative refractory period follow the Absolute and is
define as the time where the threshold to elicit an AP is much higher
than the threshold before the AP. This is because the Na channels are
changing in time from inactive to active state, allowing to an AP to be
ellicited. The repolarization time is refered to the time the membrane
voltage return to the resting level. This time is generally coincident
with the time curse of the change in potassium conductance. In
physiological (real) conditions, the highest rate are only up to 1Khz.



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