Cardiac Cycle Flashcards
7 Periods of the cardiac cylcle
Period 1 – atrial systole Only period which atria are contracted Period 2 – isovolumic contraction Period 3 – rapid ejection Period 4 – reduced ejection Period 5 – isovolumic relaxation Period 6 – rapid ventricular filling Period 7 – reduced ventricular filling
PERIOD 1
Atrial systole
Atria are contracted
Ventricles are relaxed
AV open A&P closed
PERIOD 2
Isovolumic contraction
Ventricle contract w/ NO change in volume
Atria are relaxing
AV closed A&P closed
PERIOD 3
Rapid Ejection
Ventricles are contracting
Atria are relaxed
AV closed A&P open
PERIOD 4
Reduce Ejection
Ventricles still contracting
atria still relaxed
AV closed A&P open
PERIOD 5
Isovolumic relaxation
Ventricles relaxing NO change in volume
Atria relaxed
AV closed A&P closed
PERIOD 6
Rapid ventricular filling
Ventricles relaxed
Atria not contracting to fill ventricles sucking
AV open & A&P closed
PERIOD 7
Reduced ventricular filling
Ventricles relaxed
Atria relaxed positive pressure
AV open A&P closed
A wave
Increase in atrial pressure accompanying the decrease in size of the atrial cavity and forced expulsion of blood into the ventricle
C wave
Increase in atrial pressure during isovolumic contraction
From ventricular contraction
AV valves close as ventricles depolarize
Depolarization begins at interventricular septum result is heart is temporarily shortened
Shortening forces AV valves into atria increase in atrial pressure
Subsequent contraction of the rest of ventricular myocardium results in the heart lengthening AV valves “pulled out” of atria and pressure decreases
V wave
Pressure increase in atria associated w/ venous return.
Occurs during isovolumic relaxation of ventricle
At end, AV valves open and rapid filling of ventricle begins so decrease in atrial pressure
P wave physical
period 1 of cc atrial systole
QRS complex physical
isovolumic contraction of ventricle
ST interval physical
rapid ejection phase: the ventricle is still contraction to expel blood
T wave physical
reduced ejection as the ventricle begins to relas & pressure decreases
Calculate the stroke volume from the left ventricular end diastolic volume (LVEDV) and left ventricular end systolic volume (LVESV)
Stroke volume is the diff btw LVEDV and LVESV
it represents the volume of blood discharged into circulation w/ each cycle
S1
S1 - closing of the mitral and tricuspid valves at the beginning of isovolumic contraction, LUB
S2
S2 closing of the aortic and pulmonic valves at end of cardiac cycle DUB
S3
S3 - occurs at the transition btw rapid ventricular filling and reduced ventricular feeling. Sudden tensing of the chordae tendinae. EARLY DIASTOLIC sound
pressure is increasing
S4
S4 - an abnormal noise made in the ventricles after the peak of the A wave as ventricular stenosis at the beginning of ventricular filling
S5
Opening snap (abnormal) heard in cases of mitral
Diastolic murmurs
occur after S2, but before the next S1.
Ventricles relax
Common mitral valve stenosis
Systolic murmurs
After S1 before S2
S2 marks the beginning of ventricular relaxation
Common in mitral valve regurgitation
Splitting mechanism 1
Inhalation results in expansion of the pulmonary artery, this leads to more flow through the artery
This effect increases the time that blood flows through the pulmonary valve
The result is a delayed closing of the pulmonary valve
Spitting mechanism 2
With inhalation, the favorable pressure gradient (more negative) increases venous return
The result of this is the RVEDV will be increased compared to exhalation
More time is required to empty the right ventricle
End result is pulmonary valve remains open longer
Splitting mechanism 3
With inhalation, a small amount of blood is trapped in the lungs, this is because as the lungs expand, so do the vessels in the lungs, this decreases venous return to the left side of the heart
This results in less blood being expelled from the left ventricle
Because less blood is expelled, the aortic valve closes sooner
Normal splitting
AV closes before PV
L bundle branch block & severe hypertensions
Increases the time of depolarization of the L ventricle
Impulse not traveling through fast Pfibers but the gap junctions.
R ventricle normal.
Heard on exhalation
