Why does a blood vessel downstream from a partial arterial blockage dilate, leading to reduced resistance?

💡 Explanation

A partial arterial blockage reduces blood flow, causing endothelial cells to release nitric oxide, which induces vasodilation. This is flow-mediated vasodilation because the reduced flow triggers this response rather than vasoconstriction; therefore, vessel diameter increases, reducing vascular resistance. Elevated angiotensin II would cause vasoconstriction.

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