Isovolumetric VC, Ventricular ejection, Isovolumetric & Passive ventricular filling

• Isovolumetric means that blood volume does not change. • Ventricular blood volume and cell length remain constant. • With valves closed and contraction continuing, ventricular pressure continues to rise. • Ventricular pressure rises above arterial pressure. • Increased ventricular pressure overcomes the arterial pressure and semilunar valves open. • Blood is ejected into the arteries, decreasing ventricular volume. • Ventricular repolarization (T wave) marks the end of ventricular contraction. • Ventricular pressure begins to decrease. • Initiated by repolarization of ventricular muscle cells. • Pressure in relaxing ventricle drops below arterial pressure. • SL valves are pushed closed by arterial pressure. • Dicrotic wave is produced when closure of the valves produces local pressure changes. • With all valves closed, blood volume does not change. • As the ventricle relaxes, ventricular pressure falls quickly. • Atrial pressure is greater than pressure in relaxing ventricles and AV valves open. • As the valves open the ventricles begin filling with blood. • Ventricular volume fills in about 0.2 seconds. • Atrial depolarization (P wave) will trigger atrial contraction, and a new cardiac cycle begins.

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