Physiology Rapid depolarization (phase 0) of the action potential of ventricular muscle results from opening of: A Voltage-gated Ca2+ channels B Voltage-gated Na+ channels C Acetylcholine-activated K+ channels D Inward rectifying K+ channels 💡 Explanation Rapid depolarization (phase 0) of the action potential of ventricular muscle results from opening of: ✓ Correct Answer: B. Voltage-gated Na+ channels