Final answer:
Atrial natriuretic peptides are released by cardiac atrial cells when blood volume increases and stretches those cells. This hormone release causes the kidneys to excrete more sodium and water, which lowers blood volume and blood pressure. ANP also inhibits other hormones that retain sodium and water.
Step-by-step explanation:
Atrial natriuretic peptides (ANP) are hormones produced by the heart that play a crucial role in regulating blood volume and blood pressure. These hormones are released by specialized cells located in the walls of the atria of the heart. The release of ANP is triggered by an increase in blood volume, leading to the stretching of the atrial cells. This mechanism functions as part of the body's autoregulation of circulation and blood pressure.
Here are the steps leading to the release of ANP:
- The atrial cells of the heart detect an increase in blood volume.
- The increase in volume causes these cells to stretch.
- The stretching of these cells triggers the secretion of ANP.
- ANP then promotes diuresis (excretion of urine) by causing the kidneys to excrete more sodium and water.
- The hormone also inhibits the production and release of renin, aldosterone, and antidiuretic hormone (ADH), which normally help to conserve sodium and water.
- As a result of these actions, blood volume and blood pressure decrease.
ANP has additional functions, such as acting as a vasodilator to lower blood pressure and reducing sodium reabsorption by the renal tubules. Because water passively follows sodium, ANP also has a diuretic effect. In patients with conditions such as sleep apnea, where blood pressure may be elevated, ANP can contribute to a reduction in blood pressure.