What happens to the pressure in the ventricles when they relax?

When the ventricles of the heart relax, a process known as diastole occurs. During this phase, the myocardial muscle fibers lengthen and the ventricles fill with blood from the atria. The relaxation of the ventricles leads to a decrease in intraventricular pressure. As the heart muscle relaxes, the volume of the ventricles increases, but the pressure within them drops because there is less muscular contraction exerting force against the blood. This decrease in pressure also provides the necessary pressure gradient that allows blood to flow from the atria into the ventricles, facilitating efficient filling.

The other options do not accurately reflect the physiological changes that occur during ventricular relaxation: pressure does not increase, remain the same, or fluctuate significantly; rather, it consistently decreases to enable proper filling of the heart chambers. Understanding this mechanism is critical for comprehending the cardiac cycle and the dynamics of blood flow within the heart.