Download Cardiac Cycle - Bourbon County Schools

CARDIAC CYCLE
EARLY DIASTOLE
 Pressure
in ventricles is low.
 Pressure difference causes A-V
valves to open and the ventricles to
fill.
 70% of returning blood enters
ventricles prior to contraction.
 Ventricular pressure gradually
increases.
ATRIAL SYSTOLE
 Remaining
30% of blood is pushed
into the ventricles.
 Ventricular pressure increases more.
ISOVOLUMIC VENTRICULAR
CONTRACTION
 As
ventricles contract, ventricular
pressure rises sharply.
 When this pressure exceeds atrial
pressure, A-V valves close.
 Muscles and cords prevent A-V
valves from bulging into the atria.
VENTRICULAR SYSTOLE
 A-V
valves remain closed.
 Atria are relaxed.
 Pressure in atria is low.
 Blood flows into atria from veins.
 (ventricles are contracting, atria are
filling)
 Heart sound: LUBB
PROGRESSING VENTRICULAR
SYSTOLE
 Ventricular
pressure increases.
 When it exceeds pressure in
pulmonary trunk (right side) and
aorta (left side) pulmonary and
aortic valves open.
 Blood is ejected from each valve’s
ventricle and into arteries.
BACK TO THE BEGINNING…
 Ventricular
pressure drops as
ventricles begin to relax.
 When ventricular pressure is lower
than the blood pressure in the aorta
and pulmonary trunk, pressure
difference is reversed. Valves close.
 As soon as ventricular pressure is DUPP
less than atrial pressure, the A-V
valves open and we start all over
again.
PRESSURE AND VOLUME