NLN NEX Anatomy Practice Test

During the cardiac cycle, relaxation of the heart muscle occurs in diastole. In this phase the ventricles relax and their pressure falls, the atrioventricular valves open, and blood flows from the atria into the ventricles, with atrial contraction helping to complete filling. This sets up the next contraction that pumps blood out to the lungs and to the rest of the body. Diastole is also when the coronary arteries receive blood to nourish the heart muscle itself. The other terms describe a blood component, the oxygen status of blood, or the overall circulation route, none of which describe the relaxation and filling of the heart.