AEMCA Practice Exam

Through which mechanism does angiotensin II primarily increase blood pressure?

1. By increasing heart rate

2. By vasodilation of blood vessels

3. By increasing blood volume through sodium retention

4. By contracting smooth muscle around blood vessels

The correct answer is: By contracting smooth muscle around blood vessels

Angiotensin II primarily increases blood pressure through the contraction of smooth muscle around blood vessels. This mechanism leads to vasoconstriction, which narrows the blood vessels and consequently increases the resistance that the heart must work against. As a result, blood pressure rises. Additionally, angiotensin II plays a critical role in regulating blood flow and pressure by influencing various systems within the body. It not only acts on the vascular system to cause constriction but also stimulates the release of aldosterone from the adrenal glands, which promotes sodium retention in the kidneys, thereby further contributing to increases in blood volume and blood pressure. While increasing heart rate and promoting vasodilation are processes that can influence blood pressure, they are not the primary mechanisms by which angiotensin II functions. Vasodilation is typically associated with a reduction in blood pressure, contrasting with the actions of angiotensin II. Thus, the contraction of smooth muscle around blood vessels stands out as the most direct and significant effect of angiotensin II on blood pressure elevation.