-Vasodilator metabolites are produced as a result of metabolic activity in tissue. These vasodilators are C02, H+, K% lactate, and adenosine.
- Examples of active hyperemia:
(1) If the metabolic activity of a tissue increases (e.g., strenuous exercise), both the demand for 02 and the production of vasodilator metabolites increase. These metabolites cause arteriolar vasodilation, increased blood flow, and increased 02 delivery to the tissue to meet demand.
(2) If blood flow to an organ suddenly increases as a result of a spontaneous increase in arterial pressure, then more 02 is provided for metabolic activity. At the same time, the increased flow "washes out" vasodilator metabolites. As a result of this "washout," arteriolar vasoconstriction occurs, resistance increases, and blood flow is decreased to normal.
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