Final answer:
Atrial natriuretic hormone is produced by cells in the atria of the heart in response to high blood pressure, leading to its release when the blood volume causes extreme stretching of the heart's atrial cells.
Step-by-step explanation:
Atrial natriuretic hormone (ANH), also known as atrial natriuretic peptide (ANP), is typically produced by the cells in the atria of the heart when blood volume is high enough to cause extreme stretching of the cardiac cells, which is a response to high blood pressure. This hormone functions as a powerful vasodilator and diuretic, promoting the loss of sodium and water from the kidneys, which helps to decrease blood volume and reduce blood pressure. In contrast to options such as during exercise or after meals, the hormone is not produced in response to low blood pressure or explicitly during sleep, although conditions like sleep apnea can trigger its release due to the associated fluctuations in blood pressure.