Ace the CVS Pharmacy Exam 2025 - Your Prescription for Success!

The correct choice identifies that cardiac action potentials are primarily generated by the opening of fast sodium channels and slow calcium channels. The fast sodium channels play a crucial role in the rapid depolarization phase of the action potential. When these channels open, there is a swift influx of sodium ions, which leads to a rapid change in membrane potential and triggers the action potential.

In addition to the fast sodium channels, slow calcium channels contribute significantly during the plateau phase of the action potential. The slow influx of calcium ions through these channels helps maintain the depolarized state for a longer duration, which is essential for allowing sufficient time for the heart muscle to contract effectively.

This synergistic action of both channel types ensures a well-timed sequence of depolarization and repolarization, critical for the heart's rhythmic contractions. The combination of these two types of channels is what sets cardiac action potentials apart from those in other types of muscle cells or neurons, where different ion channel combinations may be involved.