Atrial natriuretic hormone is secreted from the cells of the wall of the atrium of the heart. It increases renal sodium excretion and lowers blood pressure and blood volume. When excess blood flows into the atria, the heart wall expands. As a result, ANH is secreted from the heart wall. ANH dilates the afferent arterioles and increases the glomerular filtration rate. The collecting ducts of the nephron block sodium reabsorption. Renin inhibits angiotensin secretion.