Cardiac muscle is also an endocrine tissue that produces hormones.
True
False
The correct answer and explanation is:
Correct Answer: True
Cardiac muscle is not only responsible for pumping blood but also functions as an endocrine tissue by producing hormones. The most notable hormone produced by cardiac muscle cells, specifically by the atria of the heart, is atrial natriuretic peptide (ANP). This hormone plays an essential role in the regulation of blood pressure, blood volume, and electrolyte balance.
When blood volume increases, it stretches the walls of the atria. This mechanical stretch acts as a signal that stimulates specialized cardiac muscle cells, known as myocytes, to release ANP. Once secreted into the bloodstream, ANP acts on the kidneys to increase sodium excretion and water loss in urine. By promoting this natriuresis (excretion of sodium), ANP helps to lower blood volume and blood pressure. It also suppresses the release of hormones like renin and aldosterone, which typically act to retain sodium and water.
The endocrine role of cardiac muscle extends beyond ANP. The ventricles of the heart can also secrete brain natriuretic peptide (BNP) under conditions of excessive stretch, such as in heart failure. Despite the name, BNP is primarily produced by the heart rather than the brain. Like ANP, BNP helps to reduce blood pressure and fluid overload.
The discovery that the heart functions as an endocrine organ has added to the understanding of its role in homeostasis. Hormones like ANP and BNP are even used clinically as biomarkers in diagnosing and monitoring heart conditions such as congestive heart failure.
Therefore, the statement that cardiac muscle is also an endocrine tissue that produces hormones is true, and this dual function supports both circulatory and hormonal regulation in the human body.