When does systolic blood pressure occur?

Systolic blood pressure occurs when the heart is contracting, which is during the phase of the cardiac cycle known as systole. During this phase, the ventricles of the heart contract to pump blood out into the arteries. As the blood is ejected, it creates pressure in the arteries, which is measured as systolic blood pressure. This phase is critical for understanding how blood circulates through the body and how the body maintains proper blood flow and pressure to meet its physiological needs.

The other options do not accurately describe the phase during which systolic blood pressure occurs. For instance, the heart relaxing or at rest refers to diastole, the phase when the heart chambers fill with blood; this is when diastolic blood pressure is measured. Similarly, while the heart might be dilating in relation to filling, it is not during this action that systolic pressure is produced. Understanding the distinction between these phases is crucial for grasping how the cardiovascular system operates.