THE CARDIAC CYCLE
isovolumetric contraction phase
-Occurs between closing AV valves to the opening of the semilunar valves -During this split-second period, the ventricles are completely closed chambers so the blood volume in the chambers remains constant (isovolumetric) as the ventricles contract causing a rapid rise in ventricular pressure. -The rise in ventricular pressure causes an increase in atrial pressure because the closed AV valves bulge into the atria.
Atrial systole
-follows depolarization of atria (P wave) -atria contract/compress blood into chambers -rise in atrial pressure which propels residual blood out of the atria into the ventricles -ventricles are in the last part of their diastole and have the maximum volume -atria relax >ventricles depolarize(QRScomplex)
Ventricular filling
-heart is relaxed -semilunar valves are closed/ AV valves open -blood flows into atrium and ventricles
Stroke Volume = EDV - ESV
Calculate stroke volume
Isovolumetric relaxation: early ventricular diastole
During the brief period of time following the repolarization of the ventricles (T wave of ECG), the ventricles relax. Because the blood remaining in the ventricles is no longer compressed, ventricular pressure drops rapidly. Once ventricular pressure falls below the pressure in the aorta and pulmonary trunk, blood flows back towards the ventricles from these arteries causing the semilunar valves to close. Closure of the aortic semilunar valve causes a brief rise in aortic pressure as backflowing blood rebounds off the closed aortic semilunar valve cusps (this rise begins with the dicrotic notch shown on the aortic pressure graph).
First heart sound ("lubb")
Is a low-pitched, slightly drawn out sound. Results from closing of the AV valves.
Second heart sound ("dubb")
Is a short high-pitched sound. Results from the closing of the semilunar valves.
Heart Murmurs
Unusual heart sounds that are usually due to a heart valve defect.
ventricular ejection phase
Ventricular pressure continues to rise and when it finally exceeds the pressure in the aorta and pulmonary trunk, the isovolumetric phase ends as the semilunar valves are forced open and blood is ejected from the ventricles into the aorta and pulmonary trunk.
incompetent valve murmur
What type of defect does a murmur represented by lubb-duppshhh, lubb-duppshhh suggest?
stenotic valve murmur
What type of defect does a murmur represented by lubb-shhhdupp, lubb-shhhdupp suggest?
Ventricular systole
extends from when ventricular pressure rises (above atrial pressure) closing the AV valves to closure of the aortic and pulmonary semilunar valves
cardiac cycle
includes all events associated with the blood flow through the heart during one complete heartbeat
Stroke Volume (SV)
is the volume of blood ejected by a ventricle in one contraction (during one beat).
End Systolic Volume (ESV)
is the volume of blood in a ventricle after it has contracted' i.e., the minimum volume of blood in a ventricle.
End Diastolic Volume (EDV)
is the volume of blood that collects in a ventricle during diastole, i.e., the maximum amount of blood in a ventricle.
ventricular filling (mid-to-late diastole)
label A
ventricular systole (atria in diastole)
label B
Early diastole
label C
75 bpm
the average resting heart beat
1) ventricular filling: mid-to-late ventricular diastole 2) ventricular systole: contraction ejection 3) isovolumetric relaxation: early ventricular diastole
the cardiac cycle is considered in terms of events occurring during these three periods
0.8 seconds
the length of the cardiac cycle
Systole
the period of time when a heart chamber is contracting and emptying blood
Diastole
the period of time when a heart chamber is relaxing and filling with blood
incompetent valve
valve doesn't close tightly and makes a swishing sound that is created by backward flow (or regurgitation) immediately after the valve closes.
stenotic valve
valve that is narrowed. A swishing sound is created by blood being forced through a narrowed valve immediately before the valve closes.
