Final answer:
The action that does not help return the membrane to its resting potential during an action potential is the opening of voltage-gated Na+ channels. This is because their opening causes depolarization, and they are inactivated and then reset once the cell has depolarized, thereby not contributing to repolarization or the restoration of the resting potential.
Step-by-step explanation:
During an action potential, the action that does not help return the membrane to its resting potential is B. the opening of voltage-gated Na+ channels. During the process of an action potential, the sequence of events includes:
- Depolarization, where voltage-gated Na+ channels open allowing Na+ to rush into the cell, and the membrane potential becomes more positive.
- Following depolarization, the inactivation of voltage-gated Na+ channels and the opening of voltage-gated K+ channels occur, which allows K+ to leave the cell and starts the repolarization of the membrane.
- When the membrane potential passes -55 mV again, the voltage-gated K+ channels begin to close, with the flow of K+ through K+ leak channels and the action of the Na+/K+ pump helping to restore the resting potential.
During repolarization and the return to resting potential, the opening of voltage-gated Na+ channels does not contribute. Instead, these channels are inactivated to prevent Na+ influx, and they do not open again until the membrane potential has returned near the resting potential and the channels have reset.