This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
The plateau phase of Myocardial action potential is due to 
Select and explain. 
A. Efflux of Na+, B. Influx of Ca++, C. Influx of K+, D. Closure of voltage gated K+ channels
B: Influx of Ca++
Answer: B: Influx of Ca++ 
Explanation: Ca2+ influx through more slowly opening Ca2+ channels produces the plateau phaseRef: Ganong's Review of Medical Physiology Twenty-Third Edition Page No: 491