Vascular Control I&II

Question 1

Where in the vasculature is the resistance the highest? What does it determine?

Answer 1

Arterioles. It determines the after load.

Question 2

Where in the vasculature is the blood volume the highest?

Answer 2

In the peripheral venous compartment. It has the highest compliance too.

Question 3

What determines the preload?

Answer 3

The central venous compartment. Mostly its pressure

Question 4

What does the central venous compartment refer to?

Answer 4

The volume enclosed by the right atrium and the great veins in the thorax.

Question 5

What is venous return?

Answer 5

It is the rate at which blood returns to the thorax from the peripheral vascular beds and thus is the rate at which blood enters the central venous compartment.

Question 6

When there is a volume change in the central venous compartment what happens to the pressure? What happens to the heart?

Answer 6

It changes as well and has important effects on stroke volume and therefore cardiac output.

Question 7

If you were to stop someones heart what would be the mean systemic pressure? What does this come from?

Answer 7

7 mm Hg. This comes from the amount of fluid in the vasculature.

Question 8

What effect does increasing blood volume or venous tone have on the venous function curve?

Answer 8

It shifts the curve to the right and increases cardiac output.

Question 9

What effect does decreasing blood volume or venous tone have on the venous function curve?

Answer 9

It shifts the curve to the left and decreases cardiac output.

Question 10

What can shift a Frank-Starling curve left?

Answer 10

Sympathetic response.

Question 11

What can shift a Frank-Starling curve right?

Answer 11

Heart failure or heart disfunction.

Question 12

In a steady state what can you say about CO and venous return?

Answer 12

They are equal

Question 13

What happens to mean systemic filling pressure after increasing the volume? What happens to vascular function curve?

Answer 13

Increased volume shifts the curve to the right and increases mean systemic filling pressure. Vascular function curve shifts upward.

Question 14

What is the rate of flow when determining mean systemic filling pressure?

Answer 14

The flow is zero by definition. MSFP is thus the static equilibrium pressure that would be everywhere the same throughout the entire cardiovascular system when no blood is flowing.

Question 15

Does arteriolar tone affect the MSFP?

Answer 15

No it does not. Arterioles only hold 100cc of blood while veins hold 2500cc. Only volume affects MSFP.

Question 16

What effect does arteriolar constriction have on peripheral venous pressure, central venous pressure, and venous return?

Answer 16

It increases the after load and decreases peripheral venous pressure which decreases venous return due to a decreased pressure differential.

Question 17

What effect does arteriolar constriction have on peripheral venous pressure, central venous pressure, and venous return?

Answer 17

It decreases the after load and increases peripheral venous pressure which increases venous return due to an increased pressure differential.

Question 18

What is the only way to produce a different steady state match between venous return and cardiac output?

Answer 18

Change the cardiac function curve and/or the vascular function curve. A transfusion increases MAP and CO. Positive inotropic effect shifts the cardiac function curve and steady state CO increases. Increased HR or SV would also elevate cardiac function curve.

Question 19

What happens to veins and the heart with a sympathetic response?

Answer 19

The veins constrict and the heart becomes a stronger pump. These two together cause CO and VR to increase. VR increases because the vasoconstriction increases MSFP.