Biological Systems MCAT Practice Exam

What role does angiotensin II play in the regulation of blood pressure?

1. It acts as a vasodilator.

2. It inhibits aldosterone release.

3. It stimulates the release of aldosterone.

4. It decreases heart rate.

The correct answer is: It stimulates the release of aldosterone.

Angiotensin II plays a crucial role in the regulation of blood pressure primarily by stimulating the release of aldosterone. Aldosterone is a hormone produced by the adrenal glands that promotes sodium retention and potassium excretion in the kidneys. When sodium is reabsorbed, water follows osmotically, leading to an increase in blood volume. This increase in blood volume contributes to a rise in blood pressure. In addition to its effect on aldosterone, angiotensin II also causes vasoconstriction, which means it narrows blood vessels. This vasoconstrictive effect further raises blood pressure by increasing total peripheral resistance. Moreover, angiotensin II can signal the pituitary gland to release antidiuretic hormone (ADH), which also contributes to water retention, aiding in blood pressure regulation. This understanding of angiotensin II as a key player in both stimulating aldosterone release and causing vasoconstriction highlights its importance in maintaining blood pressure homeostasis, especially in response to low blood pressure situations.