Control of Cardiac Output Flashcards
What is afterload?
The load the heart must eject blood against
~aortic pressure
What is preload?
Amount the ventricles are stretched in diastole
What is total peripheral resistance?
Resistance to blood flow offered by all the systemic vasculature
What happens to pressure of a fluid in a tube when it encounters resistance?
Increases pressure before resistance
Decreases pressure after resistance
Effects of raising TPR with CO unchanged
Arterial pressure increases
Venous pressure falls
Vasoconstriction
Effects of lowering TPR with CO unchanged
Arterial pressure decreases
Venous pressure increases
Vasodilation
Effects of raising CO with TPR unchanged
Arterial pressure increases
Venous pressure decreases
HR increases
Blood taken from venous system
Effects of lowering CO with TPR unchanged
Arterial pressure decreases
Venous pressure increases
Causes congestion in veins
How do you calculate cardiac output?
Stroke volume x heart rate
How do you calculate stroke volume?
End diastolic volume - end systolic volume
What happens in ventricular filling?
Ventricle fills until intraventricular pressure = venous pressure
The higher the venous pressure, the more the heart fills
What is the ventricular compliance curve?
Relationship between ventricular pressure and ventricular volume
What increases ventricular compliance?
Heart is dilated
What decreases ventricular compliance?
Hypertrophy - thicker ventricle walls
What is the Frank-Starling law of the heart?
The more the heart fills, the harder it contracts
The harder the heart contracts, the bigger the stroke volume
An increase in venous pressure will fill the heart more