CARDIAC CYCLE NEWEST SUMMARY UPDATED FOR 2025 ACTUAL QUESTIONS
WITH 100% VERIFIED SOLUTIONS 2023-2025
Ventricular filling: mid-to-late diastole
Pressure is low (in left ventricle ~ 80mmHg); blood passively flows from atria through open AV
valves into ventricles from atria (SL valves closed)
Atrial depolarization triggers atrial systole (P wave), atria contract, pushing remaining 20% of
blood into ventricle
End Diastolic Volume (EDV) at rest ~ 120mL of blood
Ventricular Systole
contraction of ventricles
*AV valves slap shut at start of this phase ("lub" heart sound)
*pressure builds in the ventricles until the pressure in the ventricles exceeds the exiting arteries,
which opens the semilunar valves and blood is ejected.
*This phase of the cardiac cycle has two parts:
1. isovolumetric contraction - pressure is high enough to close the AV valves (and stop filling)
but not high enough yet to throw open the SL valves and eject blood;
2. ventricular ejection - pressure has thrown open the SL valves and blood is exiting the
ventricle.
At rest, about 70 mL of blood is ejected each pump. This is referred to as Stroke Volume. The
ejection fraction at rest is about 58% of the starting volume (in a healthy heart).
isovolumetric relaxation
When the contraction eases off, the pressure in the ventricles falls below that of the large
exiting arteries and allows the SL valve to close. But pressure is still too high in the ventricle for
, the AV valves to open. So during this period all four valves are closed and ventricular blood
volume does not change, but pressure is rapidly dropping in the ventricles.
*At the start of this phase, we hear "dup" which is the second heart sound (S2), and indicates
the closing of the SL valves.
heart murmur
abnormal heart sound.
It's often the result of an AV or SL valve that is not closing fully or properly.
Stroke Volume (SV) defined and equation
The amount of blood pumped out of the heart with each contraction.
SV = EDV - ESV
End Diastolic Volume (EDV)
Volume of blood in the ventricles at the end of diastole ("preload")
End Systolic Volume (ESV)
volume of blood remaining in each ventricle after systole
WITH 100% VERIFIED SOLUTIONS 2023-2025
Ventricular filling: mid-to-late diastole
Pressure is low (in left ventricle ~ 80mmHg); blood passively flows from atria through open AV
valves into ventricles from atria (SL valves closed)
Atrial depolarization triggers atrial systole (P wave), atria contract, pushing remaining 20% of
blood into ventricle
End Diastolic Volume (EDV) at rest ~ 120mL of blood
Ventricular Systole
contraction of ventricles
*AV valves slap shut at start of this phase ("lub" heart sound)
*pressure builds in the ventricles until the pressure in the ventricles exceeds the exiting arteries,
which opens the semilunar valves and blood is ejected.
*This phase of the cardiac cycle has two parts:
1. isovolumetric contraction - pressure is high enough to close the AV valves (and stop filling)
but not high enough yet to throw open the SL valves and eject blood;
2. ventricular ejection - pressure has thrown open the SL valves and blood is exiting the
ventricle.
At rest, about 70 mL of blood is ejected each pump. This is referred to as Stroke Volume. The
ejection fraction at rest is about 58% of the starting volume (in a healthy heart).
isovolumetric relaxation
When the contraction eases off, the pressure in the ventricles falls below that of the large
exiting arteries and allows the SL valve to close. But pressure is still too high in the ventricle for
, the AV valves to open. So during this period all four valves are closed and ventricular blood
volume does not change, but pressure is rapidly dropping in the ventricles.
*At the start of this phase, we hear "dup" which is the second heart sound (S2), and indicates
the closing of the SL valves.
heart murmur
abnormal heart sound.
It's often the result of an AV or SL valve that is not closing fully or properly.
Stroke Volume (SV) defined and equation
The amount of blood pumped out of the heart with each contraction.
SV = EDV - ESV
End Diastolic Volume (EDV)
Volume of blood in the ventricles at the end of diastole ("preload")
End Systolic Volume (ESV)
volume of blood remaining in each ventricle after systole
