Emergency Medical Technician (EMT) Intermediate Practice Exam

What occurs when systemic vascular resistance decreases?

1. Heart rate increases

2. Systolic blood pressure rises

3. Systolic blood pressure falls

4. Peripheral vascular resistance increases

The correct answer is: Systolic blood pressure falls

When systemic vascular resistance decreases, it implies that the blood vessels are dilating, allowing blood to flow more freely and easily through the circulatory system. This reduction in resistance can lead to a decrease in systolic blood pressure. As the heart pumps blood, the pressure exerted on the arterial walls is directly related to the resistance that the blood encounters. When resistance drops, the resulting flow is less constricted, so the blood pressure within the arteries diminishes, leading to a fall in the systolic blood pressure reading. This physiological response can occur in several situations, such as vasodilation, which can be influenced by factors like certain medications, increased body temperature, or hormonal changes. In contrast, the other options relate to different physiological responses that do not occur with decreasing systemic vascular resistance. For instance, an increase in heart rate might occur as a compensatory mechanism to maintain cardiac output if blood pressure were to fall, but this is not a direct result of decreased resistance itself. Systolic blood pressure rising would contradict the effects of reduced resistance, and an increase in peripheral vascular resistance would typically occur when systemic vascular resistance declines, so that option does not logically follow from the scenario presented.