Which of the following regulates blood pressure through sodium and water balance?

The correct answer highlights the role of both aldosterone and ADH (antidiuretic hormone) in the regulation of blood pressure through sodium and water balance.

Aldosterone is a steroid hormone produced by the adrenal cortex. It promotes sodium reabsorption in the kidneys, specifically in the distal convoluted tubule and collecting ducts. When sodium reabsorption increases, water follows osmotically, leading to an increase in blood volume, which in turn raises blood pressure.

ADH regulates water balance by increasing water reabsorption in the kidneys, primarily in the collecting ducts. When the body is dehydrated or blood pressure is low, ADH is released from the posterior pituitary gland. This causes the kidneys to reabsorb more water back into the bloodstream, reducing urine output and helping to elevate blood volume, leading to an increase in blood pressure.

By working through different mechanisms—aldosterone focusing on sodium reabsorption and ADH on water reabsorption—both hormones effectively contribute to the overall control of blood pressure through the regulation of blood volume. This synergistic action of aldosterone and ADH makes the response to blood pressure regulation more robust and balanced.