Final answer:
The highest blood pressure in the cardiac cycle occurs during the systolic phase, specifically during isovolumic contraction when the ventricles contract and build pressure before blood is ejected into the arteries, which is reflected in the higher systolic reading of a blood pressure measurement (e.g., 120/80 mm Hg).
Step-by-step explanation:
The highest blood pressure in the cardiac cycle will be recorded during the systolic phase. During systole, ventricular contraction occurs, which pushes out the blood and elevates the blood pressure. This is particularly evident during isovolumic contraction, where the ventricles contract but the blood hasn't been ejected yet since the pressure is not high enough to open the semilunar valves. As the ventricles continue to contract, the blood pressure quickly rises, causing the valves to open, and blood is ejected into the arteries. The pressure during systole is the higher number reported in a blood pressure measurement, for example, 120 mm Hg in a reading of 120/80.
Conversely, the diastolic phase, atrial contraction, and ventricular relaxation phases show lower blood pressure, as they are associated with the heart relaxing and refilling with blood. The diastolic pressure is the lower number in a blood pressure reading, such as the 80 mm Hg in 120/80.