1
$\begingroup$

I know, I know this is probably a question too simple to be asked on a forum like biology stack exchange. Problem is, I looked many places and can't seem to find a more mathematical approach to explain why the contraction of a BV leads to increased blood pressure (BP). The main formula i'm looking at is Flow = Pressure/Resistance. In addition, Flow = Area x velocity so Area x velocity = Pressure/Resistance. As the BV constricts, the radius, ie. area, decreases, and so the pressure decreases. But clearly, that is not the case.

What am I missing here?

| improve this question | |
$\endgroup$
  • 1
    $\begingroup$ Basic physiology questions are my personal favourite +1...anyways have you tried it this way (I'm supposing):area decreases, so flow decreases (possibly because resistance (R) increases in the blood vessel)...now to keep the flow constant the pressure (P) needs to be increased...what I 'm trying to say is that P increases to counter reduced flow as R increases. $\endgroup$ – user 33690 Apr 17 '18 at 7:50
2
$\begingroup$

There is an important missing assumption in your statement, I've added it in italics:

Contraction of blood vessels leads to increased blood pressure if total flow stays constant.

All you need is your first equation:

Flow = Pressure/Resistance

Decreasing the radius increases the resistance. If flow is constant, then pressure has to increase to get the same flow through the smaller vessel.

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.