CDCA Local Anesthesia Practice Exam

During the depolarization phase of a neuron, the key event is the influx of sodium ions (Na+) into the neuron. This occurs when voltage-gated sodium channels open in response to a stimulus, allowing Na+ to flow into the cell down its concentration gradient. As sodium enters, it causes the inside of the neuron to become more positively charged compared to the outside, which is critical for the generation of an action potential.

Potassium ions (K+) do play a crucial role in the overall action potential; however, during depolarization specifically, K+ is not exiting the neuron. Instead, it is during the later phase of the action potential, termed repolarization, that potassium channels open and K+ exits the cell to help restore the resting membrane potential.

Thus, the correct choice highlights the significant role of sodium entering the neuron during depolarization, establishing the foundation for nerve impulse conduction.