Question

Voltage-gated Na⁺ channels are membrane channels that open?

1) when the membrane is at the resting membrane potential
2) when the membrane depolarizes
3) when TTX is applied to the membrane
4) when lidocaine is applied to the membrane

Answer 1

Voltage-gated Na+ channels open when the membrane depolarizes, allowing Na+ ions to enter the cell and causing depolarization.

Step-by-step explanation:

Voltage-gated Na+ channels open when the membrane depolarizes. When the cell is at rest, the activation gate of the voltage-gated Na+ channel is closed and the inactivation gate is open. However, when the membrane potential reaches the threshold, the activation gate opens, allowing Na+ ions to rush into the cell and causing depolarization. After depolarization, the inactivation gate closes, preventing further entry of Na+ ions. When the membrane potential returns to the resting state, the activation gate closes and the inactivation gate re-opens, preparing the channel for the next action potential.