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7.While at rest, the whole body extracts approximately 25% of the oxygen from its arterial blood flow, and the myocardium extracts approximately what percentage?a.40%b.50%c.60%d.70%ANS: DEven at rest, the myocardium extracts approximately 70% of the oxygen from its arterial blood flow, compared with a 25% extraction rate for the whole body.DIF:RecallREF:3078.Which of the following is the most important factor governing coronary blood flow?
DIF:RecallREF:3089.During which part of the cardiac cycle does most coronary perfusion occur?DIF:RecallREF:308-30910.Which of the following statements are true of the sinoatrial node?I. It is embedded in the right atrial muscle.II. It is near the superior vena cava.III. It initiates the electrical impulses that produce sequential atrial and ventricular contraction.IV. It is near the right ventricle.DIF:RecallREF:30911.Which of the following is the main type of adrenergic receptor in the heart?a.b.1c.2d.NicotinicANS: BSympathetic fibers are distributed throughout the entire heart. Cardiac sympathetic receptors are mainly of the 1type.DIF:RecallREF:31012.Which of the following is the preferred biomarker for diagnosing acute myocardial infarction?
DIF:RecallREF:31313.How soon do levels of troponins rise after a myocardial infarction?DIF:RecallREF:313