Question

What causes the depolarization phase of an action potential? (Circle all that apply.)

K+ leaving the cell through voltage-gated channels

K+ being pumped into the cell by the Na+-K+-ATPase

Na+ being pumped into the cell by the Na+-K+-ATPase

Na+ entering the cell through voltage-gated channels

opening of the Na+ channel inactivation gate

Answer 1

The depolarization phase of an action potential is primarily caused by Na+ entering the cell through voltage-gated channels, leading to a reversal of the membrane potential.

Step-by-step explanation:

The cause of the depolarization phase of an action potential is primarily due to Na+ entering the cell through voltage-gated channels. When the membrane potential reaches the threshold, voltage-gated sodium channels open, and sodium ions (Na+) rush into the neuron. This rapid influx of Na+ reverses the polarity of the neuron's membrane potential, causing the inside to become more positive relative to the outside, which is the essential feature of depolarization. Another critical event during depolarization is the opening of the Na+ channel activation gate; meanwhile, the Na+ channel inactivation gate, which temporarily closes following depolarization, prevents further Na+ entry and thus contributes to the subsequent repolarization phase.