Page 2, O2 Uptake, Exercise & Cor. Circ., Dr. D. Penney


Oxygen Uptake (continued..):

Different organs receive different fractions of the cardiac output. At rest, the kidneys, abdominal viscera, and skeletal muscle each receive approximately 25% of the cardiac output. The coronary circulation of the heart receives about 5-7% of cardiac output, the brain about 3-fold that amount.

A-V O2 difference can increase considerably for some tissues during periods of maximal O2 utilization (Figure 3.01). This is true, for example, for skeletal muscle. The heart however has only a very limited ability to increase A-V 02 diff., mainly because it is already so high; to increase it further would mean than areas of the myocardium would become hypoxic. Thus, to increase oxygen delivery the heart must increase blood flow.


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