A&P Neurophysiology Practice Test 2025 – Complete Exam Preparation

The primary effect of the influx of sodium ions (Na+) during depolarization is that it increases the positive charge inside the cell. When a neuron is stimulated, voltage-gated sodium channels open, allowing Na+ ions to flow into the cell. This influx of positively charged ions reduces the negative charge inside the neuron, leading to a more positive membrane potential. As a result, the inside of the cell becomes less negative compared to the outside, transitioning the membrane potential towards a threshold that can trigger action potentials.

This process is crucial for the generation and propagation of nerve impulses. When enough sodium ions enter, it can lead to sufficient depolarization to initiate an action potential, allowing the electrical signal to travel along the axon.

In contrast, options discussing hyperpolarization, becoming more negative, or stabilizing the resting potential do not accurately describe the effects of Na+ influx during depolarization, as those processes involve different mechanisms that occur at distinct phases of the action potential or when the cell is returning to its resting state.