Effect of vasoconstriction and dilation on blood pressure

[Jmiz]

One way to regulate blood pressure is through vasoconstriction which in turn increases peripheral resistance, but also decrease the amount of blood that passes through the vessel. These two changes have opposite effects on blood pressure. So is it because the resistance increase effect lead to a greater increase of bP than the effect of having lower volume of blood passing through the constricted vessel, which would in turn decrease bP since less volume lead to less vapor pressure from blood that would act on the vessel walls?

Also since blood flow = velocity times cross area of vessel, what is the impact on blood flow due to vasoconstriction?

Since bP = force exerted on vessel walls by blood, wouldn't bP not be equal at the site of vasoconstriction compared to another unconstricted site?

Thanks

 

[stedwards]

If you constrict some veins or arteries, where does the blood go?

 

[Jmiz]

Ultimately, still back to the heart

 

[stedwards]

Blood is effectively incompressible. If the volume in reduced is some region, it has to go somewhere.

 

[Andy Resnick]

One way to regulate blood pressure is through vasoconstriction which in turn increases peripheral resistance, but also decrease the amount of blood that passes through the vessel. <snip>

There are multiple mechanisms to regulate blood pressure- not just through modulating the peripheral resistance (primarily the arterioles), but also by control over total blood volume. Hormonal control (vasoactive substances) are one mechanism, but there are many including neuronal and local autoregulation. A primary cause of hypertension is increased fluid volume due to excessive resorption of Na in the kidney, which over time leads to increased peripheral resistance.

There are multiple ways to induce high blood pressure: holding blood volume constant and increasing the peripheral resistance, or holding the peripheral resistance constant and increasing blood volume.