What physiological response occurs when atrial stretch receptors are activated?

When atrial stretch receptors are activated, they primarily lead to the release of atrial natriuretic peptide (ANP). This response is a crucial means by which the body regulates blood pressure and fluid balance. Atrial stretch receptors are sensitive to changes in blood volume; when they detect increased stretch due to higher blood volume, they stimulate the heart to release ANP.

ANP has several physiological effects; it promotes vasodilation, increases the glomerular filtration rate (GFR) in the kidneys, and encourages natriuresis, the excretion of sodium through urine. This ultimately leads to a reduction in blood volume and blood pressure, counteracting the effects of fluid overload.

The physiological role of ANP is significant in the context of heart failure and conditions characterized by volume overload. By promoting sodium and water excretion, ANP plays a key role in maintaining homeostasis and preventing complications from elevated blood pressure.

In contrast, the stimulation of the Renin-Angiotensin-Aldosterone System (RAAS), an increase in heart contractility, or a decrease in blood volume would not be the primary responses associated with the activation of atrial stretch receptors under conditions of increased blood volume. In fact, activation of these receptors