3. Cardio- Venous Return

Question 1

Venous return

Answer 1

During exercise, venous return increases. Active mechanisms are needed to help venous return:

• Skeletal pump: when the muscles contract and relax they press on the nearby veins, causing a pumping effect and squeezing the blood towards the heart
• the respiratory pump: when muscles contract and relax during the inspiration and expiration process, pressure changes occur in the thoracic and a nominal cavities. These pressure changes compress the nearby veins and assist blood return back to the heart.
• valves- prevent backflow of blood
• a thin layer of smooth muscle within the veins help squeeze blood back towards the heart
• gravity helps the blood return to the heart from the upper body

Question 2

The impact of blood pressure on venous return (systolic and diastolic)

Answer 2

When systolic blood pressure increases, venous return increases because the pressure in the blood vessels is higher, causing the blood to travel more quickly. When systolic pressure decreases, venous return decreases because the pressure in the various blood vessels has dropped, causing blood flow to reduce

Venous return is determined by the pressure gradient:
-> venous pressure(Pv)-right atrial pressure(Pra)
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Venous vascular resistance(Rv)

To simplify-
•increasing right atrial pressure decreases venous return
•decreasing right atrial pressure increases venous return