This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Conducting System of Hea, Subject name: Physiology
[{'content': 'Fastest conducting pa in the hea is: \nSelect and explain. \nA. Atrial muscle, B. Ventricular muscle, C. Bundle branches, D. Purkinje fibers', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Purkinje fibers are the fast conducting pa of the hea. It exhibit the following propeies: (1) Rapidly depolarizing fibers, (2) large diameter of fibers (largest in hea), and (3) high number of gap junctions between cells. These propeies make Purkinje fibers the fastest conducting pa in hea. Rapid conduction benefits the ventricular contraction. Since impulse spreads very rapidly, all fibers are excited almost simultaneously; all fibers of both ventricles contract together.', 'role': 'assistant'}]