The Cardiac Cycle Flashcards
when do heart valves make a sound?
when they shut and not when they open
roughly how long are diastole and systole?
at HR of 75 beats/min
diastole is 0.5 seconds
systole is 0.3 sec
what are the 5 major events in the cardiac cycle?
- passive filling
- atrial contraction - when the atria depolarise
- isovolumetric ventricular contraction
- ventricular ejection
- isovolumetric relaxation
what proportion of the ventricle filling is by passive filling?
80%
how does passive filling arise?
the pressure in the atria and ventricles is close to zero however, there is a small pressure gradient which means that blood flows from the atria to the ventricles
what is the aortic pressure in passive filling?
around 80 mmHg
what are the pressures like in the right side of the heart?
much lower
between which two waves of the ECG do the atria contract?
P wave and QRS
when does ventricular pressure increase?
ventricular contraction after QRS signal
when do the valves shut?
when the ventricular pressure exceeds atrial pressure
what causes the steep incline in ventricular pressure?
The aortic valve is still shut, so no blood can enter or leave the ventricle
The tension rises around a closed volume “Isovolumetric Contraction”
when does the ventricle eject?
when the ventricular pressure exceeds the aorta/pulmonary artery pressure. This pressure is what enables the blood to flow upwards
what makes the aortic/pulmonary valves close?
when the ventricles relax and the ventricular pressure falls below aortic/pulmonary pressure making the valves shut
what does the valve vibration cause in the pressure curve ?
the dicrotic notch
what does the closure of aortic/pulmonary valves signal?
the start of isovolumetric relaxation
