The Cardiac Cycle Flashcards
(20 cards)
define systole
ventricles contract and pump blood into aorta (LV) and pulmonary artery (RV)
define diastole
ventricles and fill with blood
list the 5 stages of the cardiac cycle
- passive filling
- atrial contraction
- isovolumetric ventricular contraction
- ventricular ejection
- isovolumetric ventricular relaxation
what happens during passive filling
low atrial and ventricular pressures (aortic valve is closed)
AV valves open - ventricles fill with blood from venous return
Right side is similar (pulmonary artery and RV pressure is lower than left side)
ventricles 80% full
during passive filling which valves are open and shut and what are the pressures of the atriums and ventricles
AV open
aortic and pulmonary valve is shut
A and V pressures are low
what happens during atrial contraction
completes EDV - pushes rest of blood in
what represents atrial contraction on an ECG
P wave
when do atriums contract on an ECG
between P wave and QRS complex
what happens during isovolumetric ventricular contraction
ventricular pressure rises
ventricle pressure exceeds atrial and AV valves shut
aortic valve still shut (no blood can enter or leave)
tension increases over closed volume
ventricular pressure rises steeply
during isovolumetric ventricular contraction what is happening with the valves and pressures
ventricular pressure rises and exceeds atrial
AV valves shut
aortic and pulmonary valves still shut
closed box - allows ventricular pressure to rise steeply
what happens during ventricular ejection
ventricular pressure rises above aorta/pulmonary arteries
aortic and pulmonary valves open
aortic pressure rises
ventricles relax and pressure falls
when it falls below aortic and pulmonary arteries pressure, valves shut
what happens to valves and pressures in ventricular ejection
ventricular pressure exceeds pulmonary/aortic artery pressure
aortic/pulmonary valves open
ventricle relaxes and pressure falls (below aortic and pulmonary)
aortic/pulmonary valves close
aortic pressure rises
when does isovolumentric ventricular contraction happen in relation to an ECG
after the QRS complex
what represents ventricular ejection on and ECG
T wave
how is stroke volume calculated
EDV-ESV
what happens during isovolumetric ventricular relaxation
starts with closure of aortic/pulmonary valves
AV valves still shut (V closed box)
tension falls around closed fall and V pressure falls
when V pressure falls below A, AV valves open
new cycle begins
what happens to the valves and pressure during isovolumetric ventricular contraction
AV valve is still shut and pulmonary/aortic valves are shut
pressure falls below aortic
AV valves open
what causes ‘lub’ - the first heart sound
shutting of AV valves in isovolumetric ventricular contraction
what causes ‘dub’ - the second heart sound
when aortic/pulmonary valves shut during ventricular ejection
what events are silent during the cardiac cycle
opening of valves
