The Cardiac Cycle Flashcards
What are the stages in the cardiac cycle?
- Late diastole
- Atrial systole
- Isovolumic ventricular contraction
- Ventricular ejection
- Isovolumic ventricular relaxation
Late diastole phase
Both sets of chambers are relaxed and ventricles fill passively
Atrial systole phase
Atrial contraction forces a small amount of additional blood into ventricles
Isovolumic ventricular contraction phase
First phase of ventricular contraction pushes AV valves closed but does not create enough pressure to open semilunar valves
Ventricular ejection phase
As ventricular pressure rises and exceeds pressure in the arteries , the semilunar valves open and blood is ejected
Isovolumic ventricular relaxation phase
As ventricles relax, pressure in ventricles falls, blood flows back into cusps of semilunar valves and snaps them closed
What does the P wave correspond to?
Atrial depolarisation
What happens to the pressures and volumes in the heart as the P wave occurs?
- Atria contracts causing increase in atrial pressure
- This is late diastole and the last bit of blood is forced into the ventricle.
- This increases ventricular volume and ventricular pressure slightly
What does the QRS complex correspond to?
Ventricular depolarisation
What occurs alongside the R in the QRS complex?
Mitral valve closes
What occurs alongside the S of the QRS complex?
Aortic valve opens
What takes place between the R and the S of the QRS complex?
Isovolumetric contraction
Isolvolumetric contraction
- Contraction of the ventricle occurring when all valves are shut
- This results in an increase in ventricular pressure but the ventricular volume remains constant
When does the aortic valve open?
When the pressure in the ventricle exceeds the pressure in the aorta
What is the dicrotic notch?
A small drop in aortic pressure coinciding with the closure of the aortic valve
Why does aortic pressure not continue to fall at the same rate following the dicrotic notch?
Blood cannot flow back into the ventricle but there is now a struggle to force the blood through the arterioles
What occurs between the aortic valve closing and the mitral valve opening?
-Isovolumetric relaxation
Isovolumetric relaxation
- Relaxation of the ventricle occurring when all the valves are shut
- Results in a decrease in ventricular pressure while the ventricular volume remains constant
What does the T wave correspond with?
Ventricular repolarisation
What happens to the pressures and volumes in the heart while the T wave occurs?
- Decrease in ventricular volume
- Decrease in ventricular pressure
- Increase in aortic pressure
What does the 1st heard sound coincide with?
Closure of the mitral and tricuspid valves
What does the 2nd heart sound coincide with?
Closure of the aortic and pulmonary valves
EDV
The volume in the ventricle at the end of diastole
ESV
The volume in the ventricle at the end of systole
SV
The volume of blood expelled by the ventricle in 1 contraction
Systolic pressure
The maximum pressure reached by the ventricle and aorta
Diastolic pressure
The minimum pressure reached by the aorta
Ejection fraction
SV/EDV
What should the ejection fraction be?
About 2/3
Pulse pressure
Difference between the systolic pressure and diastolic pressure?
What murmurs are heard after the 1st heart sound?
- Aortic stenosis
- Mitral regurgitation
What murmurs are heard after the 2nd heart sound?
- Mitral stenosis
- Aortic regurgitation
When would it be most likely for stenosis and regurgitation murmurs to occur together?
Septal defect
What does the a wave represent in regards to atrial pressure?
Increase in pressure due to atrial depolarisation and consequent contraction
What does the c wave represent in regards to atrial pressure?
-Increase in pressure due to mitral valve bulging into the atrium during the isovolumetric contraction of the ventricle
What does the v wave represent in regards to atrial pressure?
Increase in pressure due to the atrium filling while the mitral valve is closed
