Which statement best describes BNP's function?

• A. They promote vasoconstriction and sodium retention
• B. They increase heart rate
• C. They promote natriuresis and vasodilation, lowering blood volume and systemic vascular resistance
• D. They suppress atrial natriuretic peptide secretion

Answer: (C)

BNP is released by the ventricles when they’re stretched from excess volume. Its job is to ease the heart’s workload by promoting natriuresis and vasodilation. It acts on the kidneys to increase sodium and water excretion, which lowers blood volume. It also relaxes vascular smooth muscle, reducing systemic vascular resistance. Together, these actions decrease preload and afterload, helping to lower blood pressure. BNP also counteracts the renin-angiotensin-aldosterone system, reinforcing the volume- and pressure-lowering effects. That combination—natriuresis and vasodilation leading to reduced blood volume and systemic vascular resistance—best describes its function.