What physiological response occurs when atrial stretch receptors are activated?

When atrial stretch receptors are activated, the primary physiological response is the release of atrial natriuretic peptide (ANP). These receptors, located in the atrial walls, sense changes in blood volume and pressure. When there is an increase in atrial stretch, typically due to volume overload or increased venous return, the heart responds by releasing ANP into the bloodstream.

ANP plays a critical role in the regulation of blood pressure and fluid balance. It promotes natriuresis (the excretion of sodium in the urine), resulting in decreased blood volume and consequently a reduction in blood pressure. Additionally, ANP inhibits the renin-angiotensin-aldosterone system (RAAS), which would otherwise contribute to sodium retention and increase blood pressure.

Thus, the activation of atrial stretch receptors leads to the release of ANP, making this the correct response. Understanding this mechanism is important as it highlights the body's ability to self-regulate blood pressure and fluid homeostasis in response to increased blood volume.