This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
[{'content': 'Inward flow of Na+ in heart leads to \nSelect and explain. \nA. Plateau phase, B. Action potential, C. Repolarization, D. No Change', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. (b) Action potential(Ref: Ganong, 25th ed/p.521)To be more precise, influx of sodium ions causes depolarization of ventricular action potential. It is usually seen in the form of a rapid upstroke (spike)', 'role': 'assistant'}]