Question: Based on the model presented, which of the following statements expresses the proper relationship between osmolarity, ADH release, and urine production?
(A) As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.
(B) As tissue osmolarity rises, less ADH is released, causing less water to be excreted as urine.
(C) As tissue osmolarity rises, more ADH is released, causing more water to be excreted as urine.
(D) As tissue osmolarity rises, less ADH is released, causing more water to be excreted as urine.
Answer:
As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.
Explanation:
ADH is the hormone that triggers the formation of concentrated urine by stimulating the absorption of water from the filtrate in the kidneys. As the solute concentration (osmolarity) in the blood raises, the more of the ADH is released into the blood. ADH triggers reabsorption of water in collecting duct and distal tubules and thereby, reduces the water loss in urine. Increased reabsorption of water restores the osmolarity, blood volume, and blood pressure.
