3 Cardiac Cycle Flashcards
What is arterial blood pressure equal to?
ABP = SV x HR x TPR
What is energy of the blood equal to?
pressure x momentum
What are the 3 stages of Ventricular diastole?
isovolumetric relaxation
rapid/passive filling
atrial systole, ventricular filling
what are the 2 stages to Ventricular systole?
isovolumetric contraction
ejection
What is the P wave stimulating?
atrial contraction
What is the QRS wave stimulating?
ventricular contraction
What is the T wave stimulating?
ventricular repolarisation, and hence relaxation
What are the 2 heart sounds from?
lub - A-v valve closing
dub - aortic and pulmonary valves closing
How do we calculate stroke volume?
the difference between endiastolic and ensystolic volumes
What happens in the passive filling phase of ventricular diastole?
The atrial pressure exceeds that of the ventricles, blood pours into ventricles htrough open mitral valve, increasing pressure in the ventricle as the aortic valve is closed
What is aortic pressure like in the passive filling stage of ventricular diastole?
it is far higher than ventricular, so the aortic valve is closed
it is decreasing as the blood is moved off towards peripheral tissues
What is happening in the isovolumetric contraction phase of ventricular systole?
ventricular depolarisation (QRS) P(atrial) < P(ventricular) < P(aortic) A-V valve closes No change in LV volume small peak in atrial pressure as A-V valve pushes into atria
What is the purpose of isovolumetric contraction?
allows the ventricular pressure to rise above the aortic pressure, before opening the aortic valve
What happens to atrial pressure over ventricular systole?
decreases a bit, after push into atria during isovolumetric contaction
then increases gradually as it fills again
What is the relationship between ventricular and aortic pressure in ejection?
the valve is open, so any change will occur in both areas
Ultimately, the aortic pressure will exceed the ventricular pressure, the momentum of the blood will combat this
What causes ejection to slow?
relaxation of the ventricle stimulated by the T wave
What happens after the T wave?
ventricle relaxes
aortic valve will have to close as momentum is not enough to push blood into aorta, so this prevents backflow
isometric relaxation
What is the function of isometric relaxation?
to reduce intraventricular pressure down to below atrial pressure so it can fill again
What happens to the P wave during an increased heart rate?
the P wave moves further to the left, decreasing the distance between the P and the T wave, reducing passive filling time in ventricular diastole?
How can lost time in passive filling ventricular diastole be compensated for?
greater force of atrial contraction stimulated by the P wave can compensate
What should the relationship between right cardiac and left cardiac flow be?
equal, ideally
Why is ride side heart pressure lower than left?
pulmonary vascular resistance is low because the vessels are wider and shorter
when is aortic diastolic pressure measured?
just before the aortic valve open, the lowest aortic pressure reached
