Phase	Atria	Ventricles	AV	SL	Blood flow
Diastole	Relaxed	Relaxed	Open	Closed	Cardiac filling
Atrial systole	Contracted	Relaxed	Open	Closed	Atria → ventricles
Ventricular systole	Relaxed	Contracted	Closed	Open	Ventricles → arteries

A valve opens when pressure before it > pressure after it, and closes when pressure after it > pressure before it.