Cardiac Function Flashcards
What are TPR and MAP?
TPR: is the major source of alteration in pressure/volume
MAP: Arterial pressure is determined at any give time by volume (amount of blood in the arteries)
What does compliance refer to?
Whenever blood is removed from the arterial side of the CV system, then it goes to the venous side. Compliance results in the difference in pressure per given volume change between arteries (stiffer) and veins.
What are the major functions of the heart?
The Heart has two major functions:
1) Pump
2) Fill
There can be systolic dysfunction which is problems with the pumping and diastolic dysfunction which is to do with the filling.
What are some properties of the normal heart?
- The left ventricle is stronger than the right ventricle due to the fact that it is pumping into a higher resistance circuit although the L and R ventricles are pumping the same volume, the left ventricle is doing so with more pressure and needs to be stronger.
- The left ventricle is not more distensible than the right, because distensibility is due to compliance which depends on the thickness. The LV is far thicker than the RV and so it is less distensible.
- The pericardium can be an important determinant of ventricular compliance however in normal physiology it generally isn’t because the pericardium allows relatively friction free movement. (Some conditions in which it can be an important determinant are Tuberculosis, inflammation, pericarditis, cancers etc. )
Explain the relationship between pressure and volume in the heart.
For any given volume of blood, the pressure depends on:
- the compliance of the wall (during diastole) - active tension in the wall (during systole)
- the left ventricle has thicker (less compliant) walls than the right ventricle.
- the left ventricle can generate greater forces than the right ventricle
What are normal ranges for ESV, SV, EDV, and Early Diastolic pressure?
- ESV=75mL: If you empty the ventricle with each stroke, then there would be no stores to allow for easy variation in SV, so the ESV acts as a reserve for altering SV.
- SV= 150mL:
- EDV=150mL:
- Early-Diastolic Pressure= 5mmHg
What does a Frank Starling curve show?
As Volume increases, the ventricle produces a more forceful contraction thus generating a higher pressure.
It can have other actions, such as length and tension (in skeletal msucle) or EDV and SV.
What factors effect SV?
Stroke volume can be increased by:
- Increasing EDV
- Increasing ventricular contractility (the SV at any given EDV)
What factors affect Contractility?
Contractility can be increased as a result of:
- Sympathetic nerve activation
- Caffeine
- Adrenaline which is sympathetically implicated
But not due to:
- Parasympathetic nerve deactivation because they are not involved in contactility but rather to alter HR and conduction.
- Hypercapnia (increased partial pressure of CO2) which is usually a waste product and can also lead to acidosis.
What causes a murmur in the heart?
All murmors of the heart come from movements of the blood due to pathological conditions of the heart.
During Systole, which valves are open?
The mitral valve/aortic valve is closed and the pulmonary valve is open.
The opposite is seen in diastole
What is afterload?
- the load encountered by the ventricle as it commences contraction.
- a pressure load imposed by:
- arterial hypertension
- LV outflow tract obstruction
- Afterload means that the heart has a pressure overload on the ventricle.
What is Preload?
- the stretch on the myocyte fibres before they commence contraction
- a volume (EDV) load imposed by:
- increased venous return
- The amount of blood that the heart has to pump and is an indication of the heart’s ability to fill.
- If there are leaky valve which prevent the chambers from filling then there is an increase in preload.
