Which hormone released by the heart lowers blood pressure?

• A. Atrial natriuretic peptide
• B. Angiotensin II
• C. Epinephrine
• D. Norepinephrine

Answer: (A)

The heart can lower blood pressure by releasing a natriuretic hormone in response to atrial stretch. Atrial natriuretic peptide is released from the atrial cells when the atria are stretched from increased venous return. It acts on the kidneys to promote sodium and water excretion (natriuresis and diuresis), which reduces blood volume. It also relaxes some vascular beds and suppresses renin and aldosterone, further lowering systemic vascular resistance. The combined effect is a fall in blood pressure.

Angiotensin II, in contrast, increases blood pressure through vasoconstriction and by promoting sodium retention. Epinephrine and norepinephrine typically raise blood pressure by increasing heart rate, contractility, and vascular tone.