Question

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.

Answer 1

The rising phase of the action potential is due to Na+ flow into the cell. During depolarization, sodium ions flow into the cell through sodium channels.

Step-by-step explanation:

The rising phase of the action potential is due to:

Na+ flow into the cell

During the depolarization phase of the action potential, sodium ions (Na+) flow into the cell through sodium channels. This influx of positive charge leads to the rising phase of the action potential.

Example: When a neuron receives a stimulus, sodium channels open, allowing sodium ions to enter the cell. This increases the positive charge inside the cell, causing depolarization and the initiation of an action potential.

Answer 2

The rising phase of the action potential is due to 'Na+ flow into the cell only'. Option A is the answer.

Step-by-step explanation:

During the rising phase of the action potential, the cell membrane depolarizes, leading to the opening of voltage-gated sodium (Na+) channels. This allows an influx of sodium ions into the cell, causing a rapid increase in membrane potential. Therefore, option A is the correct answer.

As voltage-gated sodium channels open, sodium ions move down their electrochemical gradient from the extracellular fluid into the cell. This influx of positive charge contributes to the depolarization of the cell membrane, initiating the action potential. The rising phase is characterized by the increase in membrane potential toward the threshold level.

Option A is the answer.