The rising phase of the action potential is due to
A) Na⁺ flow into the cell only.
B) Na⁺ flow out of the cell only.
C) K⁺ flow out of the cell only.
D) K⁺ flow into the cell only.
E) Na⁺ flow out of the cell and K⁺ flow into the cell.

Question

Quizplus · Accepted Answer

The rising phase of the action potential is due to Na⁺ flow into the cell only. At the beginning of the action potential, voltage-gated Na⁺ channels open, allowing Na⁺ to flow from the extracellular fluid into the cell and causing depolarization of the membrane potential. This influx of positive charge leads to the rapid rise in membrane potential, which characterizes the rising phase of the action potential.

The Rising Phase of the Action Potential Is Due to