The correct option is ANF.
Explanation
Blood pressure and blood volume are regulated by hormonal feedback mechanisms involving the heart and kidneys. The primary systems involved are the Renin-Angiotensin-Aldosterone System (RAAS), which increases blood pressure, and the Atrial Natriuretic Factor (ANF), which acts as an antagonist to lower blood pressure.
Option Analysis
- ANF is Correct: ANF (Atrial Natriuretic Factor) is a peptide hormone secreted by the atrial wall of the heart in response to an increase in blood volume and pressure. It causes vasodilation (dilation of blood vessels) and thereby decreases blood pressure. It also inhibits the release of renin, acting as a check on the RAAS mechanism.
- Angiotensin II is Incorrect: Angiotensin II is a powerful vasoconstrictor. It increases blood pressure by narrowing blood vessels and stimulating the release of aldosterone.
- ADH is Incorrect: ADH (Antidiuretic Hormone or Vasopressin) primarily facilitates water reabsorption in the kidneys. However, it also acts as a vasoconstrictor, which leads to an increase in blood pressure.
- Aldosterone is Incorrect: Aldosterone acts on the renal tubules to increase the reabsorption of sodium and water. This increases blood volume and consequently raises blood pressure.
Key Takeaway
ANF is the specific hormone responsible for vasodilation and lowering blood pressure, functioning antagonistically to the blood pressure-raising effects of the Renin-Angiotensin-Aldosterone System.