Increase Blood Flow Causes Vasodilation and Vasoconstriction?

[dxcrunner]

How could increase the flow of blood (while holding pressure constant) in a very small arteries lead to vasoconstriction in some experiments but in others, it causes vasodilation? The average of all the experiments yields a net of no change in vessel diameter.

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[seminoma]

How could increase the flow of blood (while holding pressure constant) in a very small arteries lead to vasoconstriction in some experiments but in others, it causes vasodilation? The average of all the experiments yields a net of no change in vessel diameter.

Sounds like an MCAT question.

 

[dxcrunner]

This is not an MCAT question.

I understand how the metabolic theory says an increase in flood flow will cause vasoconstriction. (when there is a lack of blood flow to an area, metabolites that are vasodilators build up and cause increase vessel diameter. When flow is increased, the vasodilators are washed away and the result is vasoconstriction)

How could an increase in blood flow also cause vasodilation?

 

[Duke2018]

Blood vessels are inherently compliant, and thus with some amount of increased pressure the vessel begins to dilate, reducing the resistance and increasing flow.

The overall flow through the vessel will be determined by the interplay between this pressure-driven dilation and the autoregulation of the vessel (smooth muscle vasoconstriction).

This is not an MCAT question.

I understand how the metabolic theory says an increase in flood flow will cause vasoconstriction. (when there is a lack of blood flow to an area, metabolites that are vasodilators build up and cause increase vessel diameter. When flow is increased, the vasodilators are washed away and the result is vasoconstriction)

How could an increase in blood flow also cause vasodilation?

 

[worldbeater]

Flow refers to amount of blood in the vessel at that time, not the speed of the blood passing through it. It's a commonly confused term.

So when you vasoconstrict, you compresses the vessel, increasing the speed, but decreasing the flow (amount of blood) in the vessel at that time. When you vasodilate, you expand the vessel, you decrease the speed, but increase the flow/amount of blood in the vessel at that particular time.

Speed and flow go in opposite directions.