CVS Practice Test 2026 - Free CVS Practice Questions and Study Guide

In a non-pacemaker action potential (AP), the increase in sodium conductance is primarily due to the opening of voltage-gated Na+ channels. The M gates of these channels are responsible for allowing Na+ ions to flow into the cell, which is essential for the rapid depolarization phase of the action potential.

When there is an increase in Na+ conductance, this results from the M gates of the sodium channels opening. This opening occurs in response to membrane depolarization, leading to a substantial influx of Na+ ions and further depolarizing the membrane. This is a critical part of the action potential's upstroke, where the membrane potential rapidly becomes more positive.

As the M gates open, they actively contribute to the increase in sodium permeability (conductance), allowing a greater flow of sodium ions into the cell. This process is what triggers the rapid depolarization, crucial for the propagation of the action potential along neurons and muscle fibers. Therefore, the opening of the M gates in response to an increase in Na+ conductance plays a significant role in the dynamics of the action potential in non-pacemaker cells.