Mastering A&P Urinary System Practice Test

Antidiuretic hormone (ADH), also known as vasopressin, plays a crucial role in regulating water balance in the body. The correct answer highlights that ADH increases the permeability of the late distal tubule and cortical collecting ducts to water. This increase in permeability occurs through the action of ADH on specific receptors (V2 receptors) in the cells lining these nephron segments.

When ADH is released by the posterior pituitary gland in response to high plasma osmolarity or low blood volume, it promotes the insertion of aquaporin-2 water channels into the membranes of these cells. This allows for greater reabsorption of water from the tubular fluid back into the bloodstream, which helps to concentrate the urine and reduce water loss from the body. Consequently, when ADH levels are high, the body retains more water, which decreases urine output and helps maintain proper hydration and blood pressure.

In contrast, the other options do not accurately describe the function of ADH. For instance, ADH does not decrease permeability (as stated in the first option), nor does it have no effect on water reabsorption (as stated in the second option). Additionally, ADH is produced in the hypothalamus and stored and released