wiggers diagram, pressure volume loop

ventricular filling phase (valves open/closed, pressure, volume, key event)

AV valves open, atrial pressure is greater than ventricular pressure, volume is increasing in ventricle, artia contraction and atria depolarization (P-wave)

isovolumetric contraction

all valves closed, ventricular pressure is increasing, volume in ventrical is staying the same, ventricular depolarization (QRS complex), marks the begining of systole

ventricular ejection

SL valve open, ventricular pressure is greater than aortic, volume in ventricle is decreasing as blood goes to aorta, peak systolic blood pressure

isovolumetric relaxation 

all valves close, ventricular pressure drops, volume stays the same, ventricular repolarization (T-wave), early diastole

diacrotic notch 

small dip on the arterial pressure that occurs when the aortic valve closes after the left ventricle finishes contracting. 

what happens from a to b on the pressure volume loop

ventricular filling, volume of ventrical is increasing, pressure increases slightly, atrial ventricual valve is open

what happens from b to c on the pressure volume loop

isovolumetirc contraction, pressure increases in ventricle but volume stays the same, all valves closed

what happens from c to d on the pressure volume loop 

ventricular ejection, semilunar valves are open, volume leaves ventricles, 

what happens from d to a on the pressure volume loop 

isovolumetric relaxation, all valves closed, pressure decreases, volume remains low until AV valves open again