This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
[{'content': 'Coronary blood flow to the left ventricle increases during all Except \nSelect and explain. \nA. Early systole, B. Myocardial hypoxia, C. Stimulation of sympathetic nerves of the hea, D. Aerial hypeension', 'role': 'user'}, {'content': 'Answer: A \nExplanation: During early systole, coronary blood flow falls as coronary vessels are compressed by the contracting myocardium.A fall in PO2 has a potent vasodilator effect on coronary vessels. Adenosine released from hypoxic myocardium is also a potent vasodilator.Sympathetic stimulation increases the rate and force of contraction; the resulting increase in the rate of production of vasodilator metabolites dilates coronary vessels.Myocardial work and metabolism are increased in hypeension.Ref: Guyton; 13th edition', 'role': 'assistant'}]