Anatomy & PhysiologyQuestion 73 of 100
When does blood flow into the coronary arteries to supply the heart muscle itself?
a.During ventricular systole, when pressure is highest
b.During ventricular diastole, when the heart muscle is relaxed
c.Only during atrial contraction
d.Continuously and equally throughout the cardiac cycle
Explanation
The coronary arteries branch from the base of the aorta and fill primarily during diastole, because during systole the contracting myocardium compresses the vessels running through it. This is one reason very fast heart rates, which shorten diastole, can provoke ischemia. Atrial contraction contributes to ventricular filling, not coronary perfusion, and coronary flow is distinctly phasic rather than constant.
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