Question

The inactivation gate

A) quickly opens and closes after depolarization.
B) is coupled to the movement of the activation gate, but is much slower.
C) depends on a change of +100 mV from rest to be signaled to close.
D) depends on a loss of Na+ permeability to be triggered.
E) depends on a loss of K+ permeability to be triggered

Answer 1

The inactivation gate of a voltage-gated Na+ channel closes shortly after depolarization, timed with the peak of depolarization, and re-opens during repolarization, which helps reset the channel. It does not close due to a change of +100 mV or changes in Na+ or K+ permeability.

Step-by-step explanation:

The inactivation gate of a voltage-gated Na+ channel is part of a mechanism critical for the generation and propagation of action potentials in neurons. It closes after a specific period of time during depolarization, which is on the order of a fraction of a millisecond. This closure is timed with the peak of depolarization. Contrary to having a dependency on a change of +100 mV or a loss of Na+ or K+ permeability, the inactivation gate's closing is triggered by the initial depolarization event and helps terminate the influx of Na+. When the membrane potential returns toward negative values during repolarization, the inactivation gate eventually re-opens, and the activation gate closes, resetting the channel for the next action potential.