Venous return and heart rate regulation

Overview

Venous return and the skeletal muscle pump, respiratory pump, pocket valves, smooth muscle and gravity, the dizzy rower, the cardiac control centre, sympathetic and parasympathetic control, chemoreceptors, baroreceptors, adrenaline and intrinsic factors.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is venous return?

   Model answer

   Venous return is the flow of blood back to the right atrium through the veins. Venous return decides how much blood the heart can pump out.

2. 2

   Explain the skeletal muscle pump.

   Model answer

   Skeletal muscles squeeze the veins that run between them as they contract. The squeeze pushes blood towards the heart, and pocket valves stop it flowing back.

3. 3

   Explain the respiratory pump.

   Model answer

   Pressure changes in the chest and abdomen during breathing squeeze the large veins. The squeezing pushes blood back towards the heart.

4. 4

   What is the role of pocket valves in veins?

   Model answer

   Pocket valves are one-way valves in the veins. The valves close if blood starts to flow backwards, keeping flow towards the heart.

5. 5

   How does smooth muscle in vein walls help venous return?

   Model answer

   Vein walls contain a thin layer of smooth muscle. Venoconstriction squeezes the blood onward and reduces the volume held in the veins.

6. 6

   How does gravity affect venous return?

   Model answer

   Gravity helps return blood from the head and upper body. Blood from the legs must return against gravity, which the other mechanisms overcome.

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