This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'In a patient with a transplanted heart which of these are the reasons for increased cardiac output during exercise \nSelect and explain. \nA. Reinnervation of transplanted heart by vagus, B. Intrinsic mechanism., C. Epinephrine from medulla, D. Bainbridge reflex', 'role': 'user'}, {'content': "Answer: C \nExplanation: Cardiac transplantation results in total denervation of the donor's heart, including the donor sinus node, which usually controls heart rate after transplantation.\nDenervation causes an increase in basal heart rate due to parasympathetic sectioning (normally parasympathetic tone is greater than sympathetic tone on the heart).\n\nFurther increase in heart rate during exercise is dependent primarily on increase in plasma catecholamine concentration, e.g. from the adrenal medulla.", 'role': 'assistant'}]