Download Cardiac Cycle

CARDIAC CYCLE
Cardiac Cycle
 Refers to pattern of ;
 Systole (contraction)
 Diastole (relaxation)
 Shown by the heart in one complete cycle
 On average this 1 cardiac cycle lasts 0.8
seconds (based on 75 bpm)
Diastole
 Return of blood from venae cavae and
pulmonary veins to atria
 Causes atrial volume of blood to increase
 Eventually atrial pressure > ventricular pressure
 = AV valves are pushed open
Atrial systole
 Atria (R&L) contract simultaneously pushing
remainder of blood into ventricles
 Ventricles are still in diastole and SL valves
are closed
Ventricular systole
 Contraction of ventricles and closure of AV
valves. (‘lubb’)
 Blood pressure in ventricles > pressure in arteries
 = SL valves pushed open and blood pumped out
of heart into aorta and pulmonary arteries.
Diastole
 Higher pressure in arteries close SL valves
again. (‘dupp’)
 Cardiac cycle repeats
Heart Sounds
 Normal
 https://www.youtube.com/watch?v=xS3jX1FY
G-M
 Murmur
 https://www.youtube.com/watch?v=qCG_xoS
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