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
Answer is B. Ans. B. Voltage-gated Na+ channelsVoltage-gated Na+ channels are responsible for phase 0 in ventricular muscle. Voltage gated Ca2+ channels are responsible for phase 0 in nodal cells. The potassium channels mentioned do not play a role in mediating depolarization.