What is the difference between reactive hyperemia and active hyperemia?

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Reactive hyperaemia is the transient increase in organ blood flow that occurs following a brief period of ischaemia. Following ischaemia there will be a shortage of oxygen and a build-up of metabolic waste.

Active hyperaemia also known as Functional hyperaemia, metabolic hyperemia is the increased blood flow that occurs when tissue is active. When cells within the body are active in one way or another, they use more oxygen and fuel, such as glucose or fatty acids, than when they are not. Increased metabolic processes create more metabolic waste. The byproducts of metabolism are vasodilators. (Vasodilating metabolites: CO2, H+, K+, lactate, adenosine) Local arterioles respond to metabolism by dilatating, allowing more blood to reach the tissue. This prevents deprivation of the tissue.

answered Jul 25, 2012 by Eithan pitt Intern (1,025 points)
selected Jul 26, 2012 by Sulabh Shrestha

Reactive hyperemia: When blood supply to a tissue is blocked for sometime and then is unblocked, blood flow through the tissue increases immediately to 4-7 times.

vasocclusion --> Decreased [O2] --> Vasodilaion

Active hyperemia: When any tissue becomes highly active such as exercising muscle, gastric glands during hypersecretion or even brain during mental activity, rate of blood flow increases.

Increased Local metabolism --> Accumulation of vasodilator metabolites
--> Vasodilation

answered Jul 7, 2012 by Sulabh Shrestha Doctor of Medicine (5,553 points)