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': 'Myocardial oxygen demand depends upona) Preloadb) Afterloadc) Intramyocardial tensiond) Blood Hb concentration \nSelect and explain. \nA. ab, B. bc, C. abc, D. bcd', 'role': 'user'}, {'content': 'Answer: C \nExplanation: There are two terms to remember. Myocardial oxygen demand and myocardial oxygen supply. Hb concentration is a factor for oxygen supply.\nOxygen demand depends on the work being done. The work done is to pump the blood which is in the ventricles (preload) against the resistance in the aorta (afterload).\nSo, myocardial oxygen demand depends on\n\nRate- Directly proportional\nContractility- Directly proportional\nIntramyocardial tension- Directly proportional\nAfter load- Directly proportional\nPreload- Directly proportional\nWall thickness- Inversely proportional', 'role': 'assistant'}]