Cardiac Cycle Flashcards
What length of the cardiac cycle is ventricular/atrial systole/diastole?
Ventricular systole = 1/3
Ventricular diastole = 2/3
Atrial systole = 1/5
Atrial diastole = 4/5
What causes the mitral valve to close?
Ventricular pressures exceed atrial pressures
What is ventricular isovolumic contraction?
Ventricles begin to contract but no blood is ejected (volume remains steady); massive increase in pressure
Why does atrial pressure increase a little during ventricular isovolumic contraction?
as pressure increases in ventricles, blood will push against the mitral valve trying to go back into the LA
What causes S1?
First heart sound is associated w/ closure of AV valves and sound of blood trying to enter the ventricles hitting the closed valves
What marks the end of ventricular isovolumic contraction?
opening of the aortic valve -> ventricular pressure exceeds aorta pressure
Which part of the EKG does ventricular rapid ejection phase correlate with?
ST segment - phase 2 plateau between ventricular depolarization and repolarization (lengthens contraction of ventricles) -> closing of K (b) channels and opening of L type Ca channels
What happens to ventricular pressure and volume during ventricular rapid ejection phase?
Pressure continues to rise even after aortic valve opens and volume decreases as blood is ejected
What must occur to open a valve?
ventricular pressure must exceed diastolic pressure on each side to open the valve
What causes C wave? During what phase does it occur?
venous pulse C wave occurs during ventricular rapid ejection phase -> ventricular volume causes blood to push against AV valves (backwards pressure causes increase in venous pressure)
Where is ventricular pressure during ventricular slow ejection phase?
at or close to its peak pressure
Which part of the EKG correlates to ventricular slow ejection phase?
T wave -> beginning T wave = beginning phase; end of T wave = end of phase; ventricles begin to repolarize but are still ejecting blood at a slower rate
What causes the aortic valve to close at the end of ventricular slow ejection phase?
Aortic valve closes when ventricular pressure falls below aortic pressure
During which phase are all valves closed?
Ventricular diastole - isovolumic filling (there is no ejection and no filling occurring the ventricles)
What causes V wave? During which phase does it occur?
venous pulse V wave occurs during ventricular diastole - isovolumic filling; blood is filling the atria but cannot enter the ventricles due to closed valves (backs up into venous system)
What causes S2?
2nd heart sound at the beginning of diastole - aortic valve shuts and blood wants to fall back into the left ventricle so it hits against the valve
What causes the mitral valve to open?
ventricular pressure falls below atrial pressure causing mitral valve to open
What does aortic pressure do during rapid ventricular filling?
Aortic pressure drops a little over time as systemic circulation receives blood
What causes S3? Who is it normal to hear S3 in?
associated w/ blood entering ventricles so fast that it bumps into the walls of the ventricles; normal in children and athletes; associated w/ ventricular dilation (heart failure) in adults
What happens to ventricular volume during rapid ventricular filling (diastole)?
volume increases greatly as blood flows freely from atria to ventricles
What happens to ventricular pressure during reduced ventricular filling?
ventricular pressure is still lower than atrial (point of lowest pressure)
What begins at the end of reduced ventricular filling?
P wave (atrial systole)
During what part of the EKG do you have atrial diastole?
everything other than PR interval
What is the purpose of atrial systole?
to “top off” ventricles w/ blood; ventricular pressure and volume both slightly increase
