Vascular shunt and venous return Flashcards
What is Venous Return (VR)?
The volume of blood that returns to the RIGHT side of the heart via the veins.
Name one mechanism that aids Venous Return.
- Pocket Valves
- Muscle Pump
- Respiratory Pump
- Smooth Muscle
- Gravity
What do Pocket Valves do?
Prevent backflow of blood in veins.
How does the Muscle Pump assist Venous Return?
It squeezes veins, forcing blood back towards the heart.
What role does the Respiratory Pump play in Venous Return?
It squeezes veins in the thoracic area, forcing blood back to the heart.
How does Smooth Muscle contribute to Venous Return?
Wave-like contraction of smooth muscle in vessel walls directs blood back to the heart.
What is the effect of Gravity on Venous Return?
It pulls blood from the upper limb and head back down towards the heart.
What happens if an active cool down is not completed?
Can result in blood pooling, dizziness, or fainting.
State Starling’s Law in relation to Venous Return.
A decrease in Venous Return = A decrease in stroke volume, which = a decrease in Q.
What happens with an increase in Venous Return according to Starling’s Law?
An increase in Venous Return = An increase in stroke volume, which = an increase in Q.
What is the Vascular Shunt Mechanism?
It alters blood distribution as CO2 increases in the blood.
Which areas benefit from the Vascular Shunt Mechanism?
Muscles are the main beneficiary.
How does the blood flow to the brain change during exercise?
The brain’s blood flow is unchanged.
What happens to blood flow to the kidneys, liver, and bone marrow during exercise?
Blood flow is reduced.
According to the 80/20 Rule, what percentage of blood is distributed to the muscles during rest?
20%.
According to the 80/20 Rule, what percentage of blood is distributed to the organs during exercise?
80%.
Calculate 20% of Cardiac Output (Q) if it is 5L.
1L.
Calculate 80% of Cardiac Output (Q) if it is 5L.
4L.
What does the Sympathetic Nervous System do to the Precapillary Sphincters during exercise?
Closes the Precapillary Sphincters and vasoconstricts the arterioles at the organs.
What happens to the Precapillary Sphincters at the muscles during exercise?
They open and arterioles vasodilate.
Why is blood flow to the muscles increased during exercise?
Because less blood is sent to non-essential organs.
