Physiological Adaptation Q 27
When do coronary arteries primarily receive blood flow?
A. During inspiration
B. During diastole
C. During expiration
D. During systole
Correct Answer: B. During diastole
Although the coronary arteries may receive a minute portion of blood during systole, most of the blood flow to coronary arteries is supplied during diastole.
Option A: Breathing patterns are irrelevant to blood flow. It has been suggested that the diaphragm will preferentially steal blood flow from working locomotor muscles during increased activity (Bradley & Leith, 1978; Musch, 1993). In healthy adults, the cost of breathing is <5% of the total oxygen consumption at low-level exercise but approaches 15% during heavy exercise in young athletes or older fit subjects (Aaron et al. 1992; Dempsey & Johnson, 1992). Further, reflex vasoconstriction of the locomotor muscles is evident when a substantial respiratory load is applied sufficient to elicit diaphragm fatigue
Option C: Expiration is not related to the blood flow. The pulmonary system is intimately linked with the cardiovascular system anatomically and hemodynamically and plays a significant role in exercise intolerance through a number of mechanisms (Olson et al. 2006a,b;).
Option D: There is a little portion of the blood that the coronary arteries receive during systole. During systole, intramuscular blood vessels are compressed and twisted by the contracting heart muscle and blood flow to the left ventricle is at its lowest. The force is greatest in the subendocardial layers where it approximates to intramyocardial pressure.