What mechanism causes the voltage-gated Na⁺ channels to close during an action potential?
A)The activation gate is voltage sensitive and closes close to the equilibrium potential for Na⁺.
B)The activation gate is sensitive to K⁺ and closes when its intracellular concentrations drop.
C)The inactivation gate has a time-dependent closure.
D)The inactivation gate is voltage sensitive and closes close to the equilibrium potential for Na⁺.

Question

Quizplus · Accepted Answer

The inactivation gate of the voltage-gated Na⁺ channels is time dependent and closes shortly after the activation gate opens, thus blocking the flow of sodium ions through the channel. This ensures that the action potential depolarization phase is brief and does not continue indefinitely. Choice A and D are not correct as they refer to the activation gate rather than the inactivation gate. Choice B is not correct as the activation gate is not sensitive to K⁺.

What Mechanism Causes the Voltage-Gated Na⁺ Channels to Close During