Cardiac cycle Flashcards
cardiac cycle
all events that occur form the begginign of one heart beat to the beginning of the next
passive filling
Pressure in atria and ventricles close to zero
AV valves open so venous return flows into the ventricles
Aortic pressure ~ 80 mmHg, and aortic valve is closed
Similar events happen in the right side of the heart, but the pressures (right ventricular and pulmonary artery) are much lower
Ventricles become ~ 80% full by passive filling
atrial contraction
what signals atrial contraction in ECG
P wave
when does the atria contract
between the p wave and qrs
what completes the end diastolic volume
ATRIAL CONTRACTION
isovolumetric ventricular contraction
av valve shut so no blood can enter or leave the ventricle and tension rises around a closed volume
when does ventricular contraction strat
after the qrs
what produces the first heart sound
closing of av valves
ventricular ejection
When the ventricular pressure exceeds aorta/pulmonary artery pressure
Aortic/pulmonary valve open
ventricles relax and so the valves shut due to pressure falling
what signals ventricular repolarisation
t wave
what produces second heart sound
closure of aortic/ pulmonary valve
Isovolumetric Ventricular relaxation
Closure of aortic/and pulmonary valves signals the start of the isovolumetric ventricular relaxation
Ventricle is again a closed box, as the AV valve is shut
The tension falls around a closed volume “Isovolumetric Relaxation”
When the ventricular pressure falls below atrial pressure, AV valves open
what does the first heart sound herald
beginnign of systole
what does s2 herald
beginning of diastole
JVP
indirect measure of pressure in right atrium
when is s3 heaed
early diastolic immediately after s2
what might an s3 be assoc with in cardiac failure
Commonly left ventricular systolic dysfunction
where are s3s best heard
apex
When is an S4 heart sound heard
Late diastolic shortly before S1
when are the av valves open
during atrial contraction and ventricular systole
when do the av valves shut
when pressure in the ventricles exceeds pressure in the atria; ventricular contraction
when do the semilumar valves open
ventricular contraction
when do the semilunar valves shut
when pressure in atria exceeds pressure in ventricles; ventricular diastole
preload
ventricular wall stress at the end of diastole
what can affect preload
dilated cardiomyopathy as ventricles are dilated and stretchy
what can decrease preload
ventricular cardiomyopathy as the ventricles are stiffened
when might a fourth heart sound be heart
in ventricular hypertrophy due the stiffened wall making a vibration noise when bllod is flowed in
