Why Do Na⁺ Ions Enter the Cell When Voltage-Gated Na⁺

Question

Why do Na⁺ ions enter the cell when voltage-gated Na⁺ channels are opened in neurons?
A)because the Na⁺ concentration is much lower outside the cell than it is inside
B)because the Na⁺ ions are actively transported by the sodium-potassium pump into the cell
C)because the Na⁺ concentration is much higher outside the cell than it is inside, and the Na⁺ ions are attracted to the negatively charged interior
D)because the Na⁺ concentration is much higher outside the cell than it is inside, and the Na⁺ ions are actively transported by the sodium-potassium pump into the cell
E)because the Na⁺ ions are then able to pass through the plasma membrane unassisted

Accepted Answer

The Na⁺ concentration is much higher outside the cell than it is inside, and the Na⁺ ions are attracted to the negatively charged interior. When the voltage-gated Na⁺ channels are opened, the resulting influx of Na⁺ ions rapidly depolarizes the cell membrane and initiates an action potential.