What is the effect of depolarization on a neuron's membrane potential?

When depolarization occurs, a neuron's membrane potential becomes less negative, moving closer to zero from a resting state of around -70 mV. This process is primarily due to the influx of sodium ions (Na+) into the cell through voltage-gated sodium channels. As these positive ions enter the neuron, the internal charge of the cell becomes progressively less negative, which leads to a change in the membrane potential.

This change is crucial because it can trigger an action potential if the membrane potential reaches a certain threshold. During an action potential, if the depolarization is sufficient, it triggers the opening of more sodium channels, leading to a rapid spike in membrane potential. Therefore, depolarization is a key part of neuronal signaling and communication.

The other options do not accurately describe the effect of depolarization on membrane potential: becoming more negative does not characterize depolarization, and staying the same contradicts the very nature of what depolarization entails — a change in electrical charge — while fully depolarizing without signaling overlooks the importance of reaching that threshold needed to propagate a signal or action potential.