HTxFrog

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Jun 19, 2008
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I'm trying to figure out the cardiac and vascular function curves on pg. 252 of the 2010 First Aid and one of the changes it has says "increased TPR, e.g., exercise." Then it has the vascular function curve moved to the right (not rotated) indicating an increase in mean systemic pressure. Is that correct? BRS phys. says an increase in TPR will just rotate the vascular function curve counterclockwise, with no change in mean systemic pressure, but I guess exercise might cause venoconstriction that would account for the change. Idk, I'm confused, anybody know the answer??
 

turkeyjerky

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the venoconstriction seen in exercise will cause an increased mean systemic pressure. the tpr (which is actually reduced in exercise) will have no effect on mean systemic pressure, since this variable is measured under the experimental condition of no blood flow.
 

turkeyjerky

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yeah, the op wasn't asking about blood pressure, he's asking about the mean circulatory filling pressure
 
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mine has an arrow downwards. decreased TPR is due to the affects of increased metabolic activity in the skeletal muscle (b/c of vasodilation in the arterioles overcomes the net effect of vasoconstriction of the other systemic vessels). this is active hyperemia

also occuring is increased mean systemic filling pressure due to an increase in blood volume for venous return (you are pushing blood from arterial side to venous side). you can only increase Msp by increasing blood volume or decreasing venous compliance.

therefore, the immediate affects of exercise are increased cardiac output, increased venous return blood volume, which increases Msp, and a net decrease of TPR due to vasoD in the skeletal muscles.

increased TPR would occur in something like hemorrhage, which is shown on that same graph with a clockwise shift.

BRS talks about vascular function on pages 84-86, and effects of exercise on page 102.

hopefully this helps and i didnt mess anything up and confuse you more :)