Flashcards in Peripheral Circulation and Cardiac Output Deck (21):
the ability to distend and increase volume due to a pressure increase
How do we measure cardiac output?
Output = stroke volume x heart rate
What is TPR?
Total peripheral resistance
The sum of all arteriolar resistance
Why do we need compliance?
Compliance stores mechanical energy during systole and dissipates it gradually over diastole to dampen the pulsatile nature of the pressure wave.
How do we calculate pulse pressure and what is its normal value?
Systolic pressure - diastolic pressure
What is the difference between vasodilation and vasodilatation?
Vasodilation: no tonic vasoconstriction
Vasodilatation: offsetting vasoconstriction
What happens to TPR if blood demand increases?
If the cardiac output is constant and TPR falls what are the effects?
Arterial pressure falls
Venous pressure rises
If TPR is constant but cardiac output rises, what are the effects?
Arterial pressure increase
Venous pressure decrease
What does the ventricular compliance curve show?
The relationship between venous pressure and ventricular volume. Increasing venous pressure will increase the amount the ventricles fill.
What is Starling's Law of the Heart?
Stretching of the cardiac muscle (increased ventricular filling) increases the binding of actin and myosin and therefore the heart will contract harder.
How do we depict Starling's law of the heart on a graph?
Increased EDV/venous pressure increases stroke volume
What is contractility?
The efficacy of the heart for each contraction
What determines force of contraction?
What is meant by the term 'aortic impedance'?
The higher the pressure in the arteries, the harder it is to eject blood.
The volume of blood in the ventricles at the end of diastole (EDV)
The resistance to left ventricle must overcome to circulate blood
Why does an increase heart rate become counterproductive after a time?
Increase heart rate shortens the length of diastole therefore the heart does not fill as much and therefore the stroke volume falls. Also, the coronary arteries fill in diastole and if this is shortened they may not get adequate blood supply to perfuse the heart muscle.
What is the Bainbridge reflex?
Rise in venous pressure will be sensed in the right atrium
Decreased parasympathetic activity will increase HR to increase cardiac output
Subsides very rapidly
If resistance increases, what happens to pressure, energy loss and flow?
Energy loss increases