Introduction

The generation of an action potential is a fundamental process in neuronal communication. One of its critical phases is depolarization, which involves a rapid change in the neuron’s membrane potential from negative to positive. This phase is primarily driven by specific ion movements across the neuronal membrane. This article focuses on the ionic mechanism underlying the depolarization phase.

Ionic Mechanism of Depolarization

• Depolarization begins when a stimulus causes some voltage-gated sodium (Na⁺) channels in the neuron’s membrane to open.khanacademy+1

• Because extracellular Na⁺ concentration is much higher than intracellular, sodium ions rush into the neuron along their electrochemical gradient.

• This influx of positively charged sodium ions results in the inside of the cell becoming more positive, moving the membrane potential towards and beyond zero in the rising phase of the action potential.wikipedia+1

• The process continues in a positive feedback loop, opening more sodium channels until the peak of the action potential is reached.

Why Other Options Are Incorrect

Summary Table

Conclusion

During the generation of an action potential, depolarization is due to:

(3) Na⁺ influx