Q=P/R (help please)

[Strider_91]

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I am having a brain block trying to understand how the high resistance in arterioles leads to lower pressure because mathematically according to this formula (Q=P/R) it makes no sense to me. based on googling it seems to have something to do with resistors in parallel but I still cant quite put it together. Can someone please explain it to me as I really want to understand this and not just memorize it.

Thanks in advance.

I can also intuitively understand that pressure drops across them due to increase in cross sectional area but I just cant understand it in terms of Q=P/R because in that equation it seems to me that if Q were constant and R increased you would also need to increase pressure to keep Q the same.

 

[libertyyne]

I am having a brain block trying to understand how the high resistance in arterioles leads to lower pressure because mathematically according to this formula (Q=P/R) it makes no sense to me. based on googling it seems to have something to do with resistors in parallel but I still cant quite put it together. Can someone please explain it to me as I really want to understand this and not just memorize it.

Thanks in advance.

I can also intuitively understand that pressure drops across them due to increase in cross sectional area but I just cant understand it in terms of Q=P/R because in that equation it seems to me that if Q were constant and R increased you would also need to increase pressure to keep Q the same.

high resistance in arterioles = higher systemetic BP.
higher resistance in arterioles is due to smaller diameter, which results in greater resistance, which leads to a greater drop across the arteriole.

 

[WanderingGuitarist]

Q = Delta P / R

So if we keep Q constant and increase R, that means Delta P must increase.

Delta P in this situation would be Pressure of arteries - Pressure of arterioles.

So, you can increase delta P by increasing pressure in arteries or decreasing pressure in arterioles.

The first scenario doesn't really occur.

The second scenario, however does occur. That's why a large pressure drop across the arterioles keeps blood flow constant.

 

[Strider_91]

Q = Delta P / R

So if we keep Q constant and increase R, that means Delta P must increase.

Delta P in this situation would be Pressure of arteries - Pressure of arterioles.

So, you can increase delta P by increasing pressure in arteries or decreasing pressure in arterioles.

The first scenario doesn't really occur.

The second scenario, however does occur. That's why a large pressure drop across the arterioles keeps blood flow constant.

OOOOOOOOOOHHHHHHHHH I was neglecting the delta.

Okay this makes sense now. thank you so so much.

 

[WanderingGuitarist]

OOOOOOOOOOHHHHHHHHH I was neglecting the delta.

Okay this makes sense now. thank you so so much.

Np! Glad you understand it now 🙂

 

[watermelon master]

When I see Q = P/R, I mentally rewrite it as CO = MAP/TPR. It puts it into context and makes it easier to understand (for me at least)