Final answer:
Antidiuretic hormone (ADH), also known as vasopressin, is the hormone that boosts water reabsorption in the kidney collecting ducts, reducing urine output and elevating blood volume and pressure to maintain fluid balance and stable blood pressure levels.
Step-by-step explanation:
The hormone responsible for increasing water reabsorption by the kidney collecting duct, thus decreasing urine output and raising both blood volume and blood pressure, is known as antidiuretic hormone (ADH), also referred to as vasopressin. ADH acts on the collecting ducts of the kidneys to promote the insertion of aquaporin water channels into their cell membranes, greatly enhancing the reabsorption of water back into the bloodstream. The precise regulation of water reabsorption is vital for maintaining the body's fluid balance and ensuring stable blood pressure.
Another hormone that plays a role in fluid balance is aldosterone, which causes the kidneys' distal tubules to reabsorb more sodium (Na+), and water follows by osmosis, consequently increasing blood volume. The production of aldosterone is stimulated by angiotensin II, which is a powerful vasoconstrictor and leads to an increase in blood pressure. ADH and aldosterone work in concert to regulate the body's fluid homeostasis, impacting urine volume and blood pressure according to the body's needs.
When the body is dehydrated or when blood pressure falls, ADH secretion is stimulated, and as a result, more water is conserved, decreasing urine volume while augmenting blood volume and pressure. Conversely, when there is adequate hydration and blood pressure is normal or elevated, ADH secretion is reduced, resulting in less water reabsorption, increased urine output, and maintenance of normal blood pressure.
The hormone that increases water reabsorption by kidney collecting ducts is antidiuretic hormone (ADH); this action conserves water, decreases urine volume, and increases blood volume and pressure.