Question

Which of the following statements is false?

a. ADH increases permeability of DCT and collecting tubules to water thus decreasing urine volume.
b. An increase in aldosterone secretion results from decreased blood volume, decreased cardiac output, increased serum K+ or a decrease of serum Na+.
c. A person in chronic renal failure is likely to be in acidosis because kidneys fail to excrete H+, may be anemic because the kidneys do not produce erythropoietin and may have symptoms of hypocalcemia because kidneys do not activate vitamin D.
d. The majority of solute and water reabsorption from the glomerular filtrate occurs in the distal convoluted tubules and collecting ducts.
e. The three main mechanisms used by the body to compensate for acid-base imbalances are buffers, respiration and renal output of H+ and HCO₃

Answer 1

The false statement is that ADH increases permeability of DCT and collecting tubules to water, decreasing urine volume.

Step-by-step explanation:

The false statement is option a, which states that ADH increases permeability of DCT and collecting tubules to water, decreasing urine volume. In reality, ADH increases permeability of DCT and collecting tubules to water, increasing urine volume.

The false statement is 'd. The majority of solute and water reabsorption from the glomerular filtrate occurs in the distal convoluted tubules and collecting ducts.' as most reabsorption takes place in the proximal convoluted tubule. The roles of ADH and aldosterone are central in fine-tuning water and sodium reabsorption in the collecting ducts and distal convoluted tubules.

The statement that is false is: 'd. The majority of solute and water reabsorption from the glomerular filtrate occurs in the distal convoluted tubules and collecting ducts.' This statement is not true because the majority of water and solute reabsorption actually occurs in the proximal convoluted tubule (PCT), where approximately 70-80% of the filtrate is reabsorbed into the bloodstream. The distal convoluted tubule (DCT) and collecting ducts reabsorb a much smaller fraction of the filtrate, regulating the concentration of urine.

Antidiuretic hormone (ADH) and aldosterone play crucial roles in this process. ADH increases water permeability in the collecting ducts by stimulating the movement of aquaporin water channels to the cell membrane, leading to more water reabsorption into the bloodstream. Meanwhile, aldosterone acts on the DCT and collecting ducts to increase sodium reabsorption, indirectly leading to water retention and, hence, maintaining blood volume and pressure. Together, these hormones finely tune the reabsorption of water and solutes to maintain fluid balance and homeostasis.

A person in chronic renal failure typically exhibits symptoms such as acidosis, anemia, and hypocalcemia due to the compromised function of the kidneys in excreting H+, producing erythropoietin, and activating vitamin D, respectively. Finally, the body's compensatory mechanisms for acid-base imbalances include the use of buffers, changes in respiration, and renal output of H+ and HCO₃.