Lecture 1

Question 0

Does the pericardium play a role in compliance?

Answer 0

To a small degree, if there is pericardial filling - the compliance of the heart decreases - harder to expand

Question 1

What is compliance?
Which ventricle is more compliant?
What are the consequences of ventricular compliance in terms of normal pressure?

Answer 1

1. Compliance: the stiffness, how hard it is to expand, the harder to expand - the less compliant.
   Venous system is more compliant.
2. The right ventricle is more compliant - allows for more filling
3. Compliance is important for diastole whereas active pressure is important for systole.
   -increase compliance - increase filling - pressure doesn’t change.

Question 2

What part of the vascular system is the most compliant?

Answer 2

Venous - doesn’t change as much pressure with increased volume. Consequence: most of the blood in the body approximately 65% found in the venous system.

Question 3

What is arterial pressure?

Answer 3

Arterial pressure = MAP = CO x TPR

Question 4

What is TPR and when in the vascular system is it most prominent?

Answer 4

Total peripheral resistance. Occurs at the level of the organs - arterioles. Increase TPR causes more blood to remain on the arterial side, increasing arterial pressure.

Question 5

What does blood pressure depend on?

Answer 5

CO and TPR

Question 6

What part of the cardiac cycle do valves open or close?

Answer 6

Isovolumetric
Contraction - AV Close at the beginning/SL open at the end.
Relaxation - SL close at the beginning/AV open at the end

Question 7

Why do we have an ESV?

Answer 7

It is due to need of demand. We are primed and ready to go upon emergency. Without it - we have to wait.

Question 8

How is stroke volume increased?

Answer 8

Increased EDV
Sympathetic activity

Yet, sympathetic can also increase heart rate that decreases SV - shorter times for filling

Question 9

Does parasympathetic influence contraction?

Answer 9

No, it influences the SA/AV node, vessels, conduction pathway

Question 10

What happens during contractility?

Answer 10

The valves stay open longer due to the increased pressure thus pushing more blood out. Increasing contractility -> decreases ESV
Decrease compliance -> Increases Stiffness -> Decrease EDV

Question 11

What is Afterload?

Answer 11

Load encountered by ventricle as it commences contraction

i.e. Arterial Hypertension

Question 12

What is Preload?

Answer 12

The stretch of myocytes before contraction.

i.e. VR increase