TBR Bio 1: Ch.2 Passage 3 (Venous Return, Venous Pressure & Cardiac Output)

[remedy23]

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I get how an increase in venous return increases cardiac output

What I don't get is how can an increase in venous pressure decrease venous return, yet still increase cardiac output?

 

[chemist16]

My bio is rusty but I'm pretty sure an increase in venous pressure increases venous return. Since venous return is determined by a pressure gradient (venous pressure minus right atrial pressure).

 

[basophilic]

I get how an increase in venous return increases cardiac output

What I don't get is how can an increase in venous pressure decrease venous return, yet still increase cardiac output?

i'd interpret it as this: venous pressure increases when skeletal muscle squeezes the veins, which happens during intense exercise; so constricted veins might allow lesser blood to reach right atrium at a time; even though end diastolic volume is low (due to low venous return) in the ventricles, the increased heart rate and contractility of the heart will minimize end systolic volume and ultimately increase cardiac output (since CO also depends on heart rate)
just speculation...