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Factors ensuring that ventricular muscle has an adequate oxygen supply include the A. Good functional anastomoses that exist between adjacent coronary arteries. B. Structural arrangements that prevent vascular compression during systole. C. High oxygen extraction rate from blood circulating through the myocardium. D. Sympathetic vasodilator nerve supply to ventricular muscle. E. Fall in coronary vascular resistance during exercise. |
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Answer» A. False Coronary arteries are functional ‘end arteries’ and have few anastomotic connections; sudden occlusion of an artery usually leads to local muscle death. B. False Coronary vessels are compressed by the contracting myocardium in systole. C. True The extraction rate is about 75 per cent. D. False Reflex vasodilatation is not important in regulating coronary blood flow. E. True The rise in metabolic activity in the exercising heart provides the vasodilator metabolites which adapt coronary flow to supply myocardial oxygen needs. |
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