Final answer:
True, The dicrotic notch occurs when the semilunar valves, including the pulmonic valve, close during the isovolumic ventricular relaxation phase of early ventricular diastole, preventing backflow of blood into the heart. This is a true statement.
Step-by-step explanation:
The statement that the dicrotic notch occurs when the pulmonic valve closes is True. During the isovolumic ventricular relaxation phase, which is the initial phase of ventricular diastole, the semilunar valves, which include the aortic and the pulmonary or pulmonic valves, close to prevent blood from flowing back into the heart from the two major arteries. This closure of the semilunar valves is what produces the dicrotic notch, a small dip seen in blood pressure tracings, reflecting the brief increase in aortic pressure as blood rebounds off the closed valves.
This physiological event is crucial in understanding the dynamics of the cardiovascular system and heart function. The closure of the atrioventricular valves during the ventricular systole prevents the backflow of blood into the atria, while the closure of the semilunar valves during early ventricular diastole prevents backflow into the ventricles, indicating a well-coordinated process ensuring one-way blood flow through the heart.