Biology / Unit 12 Bio 2823 short lesson, about 20 seconds
Action Potential
Captions available
The idea
An action potential is a brief, all-or-nothing reversal of membrane potential: once a stimulus depolarizes the membrane to a threshold near −55 millivolts, sodium channels open and the neuron fully depolarizes.
In practice
After peak depolarization, voltage-gated potassium channels open, repolarizing the membrane and briefly overshooting into hyperpolarization.
Where people slip
An action potential is "all-or-nothing" — a neuron reaching threshold always fires fully, never partially.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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