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During Depolarization the Sodium VGC open when they receive the Threshold Stimulus. But when Repolarization occurs there comes a point when the cell interior has exactly the the same potential that it had during Depolarization i.e.,60mV but the Sodium VGC remain closed. Am I getting something wrong? If no, please explain.

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Voltage-gated sodium channels have three basic states that represent different conformations of the protein: closed, open, and inactivated.

When a voltage-gated sodium channel is open at depolarized voltage, there is space for part of the channel to shift into a position that blocks the pore. When this happens, it gets stuck blocking the flow of sodium, and it requires a negative membrane potential to remove the block. We call this the "inactivated" state, and this model is called the ball and chain model of sodium channel inactivation.

The inactivation gating process is also referred to as the "h-gate", because h is the variable representing the gating in the classic Hodgkin-Huxley model.

Wikipedia currently has a useful table on the sodium channel page showing the different states that a sodium channel goes through during different phases of an action potential.

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