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

Multiple Choice

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