Final answer:
The hormone released from the atria in response to chamber distension is the atrial natriuretic peptide (ANP). ANP acts to reduce blood volume and pressure by promoting the excretion of sodium and water in the urine and suppressing other hormones that regulate fluid retention.
Step-by-step explanation:
The hormone that is released from the atria in response to distension of these chambers is known as the atrial natriuretic peptide (ANP), sometimes also referred to as atrial natriuretic hormone (ANH). When the body experiences an increase in blood volume or pressure, the cells of the heart's atrial wall become stretched. This triggers specialized endocrine cells within the atrial walls to produce and release ANP.
ANP acts on the kidneys to decrease the reabsorption of sodium (Na+), leading to a loss of both Na+ and water in the urine. As a result, this promotes a decrease in blood volume and blood pressure. Additionally, ANP suppresses the production and release of hormones like renin, aldosterone, and antidiuretic hormone (ADH), which further contributes to fluid loss from the body and the reduction of blood pressure.