Question

How is the amount of urine produced regulated?
A) By ACTH (adrenocorticotropic hormone)
B) By ADH (antidiuretic hormone)
C) By ADH and regulation of blood volume
D) None of the above

Answer 1

Hint: There are several feedback loops that regulate urine volume. These are linked to the dissolved electrolytes, blood volume, and a few hormones. Weather conditions can also affect urine volume.

Complete Answer:
- Adrenocorticotropic hormone is produced by the pituitary gland in response to various stress factors. ACTH then acts on the adrenal glands that are situated above the kidneys, stimulating them to produce and release cortisol, the stress hormone. Option A is not the correct answer.
- Antidiuretic hormone or ADH is released by the pituitary glands when blood volume falls. ADH acts on the distal convoluted tubules in the nephron, increasing the reuptake of water from the kidneys. That will therefore reduce the total amount of urine produced. Option B is correct.
- Blood volume plays a role in urine production as well. When the blood volume falls too low, it stimulates more reuptake of water in the distal convoluted tubules. When blood pressure is higher due to increased volumes of blood, the amount of water filtered out in the glomerulus increases. Therefore ADH and regulation of blood volume both play a role in regulating the volume of urine produced. The correct answer to this question is option C.

Hence the correct answer is option C.

Note: The other factors that affect urine volume include the amount of water being lost as sweat particularly in hot weather or during intense physical activity. High salt diets increase urine production as $Na^+$ needs sufficient water of solution to be excreted efficiently.