Scientists Studied the Thermoregulatory and Osmoregulatory Responses in Exercising Human

Multiple Choice

Scientists studied the thermoregulatory and osmoregulatory responses in exercising human subjects who were experiencing different levels of dehydration (0%, 3%, 5%, and 7% based on body weight) . After exercise, the subjects' body temperatures, sweating rates, and blood solute concentrations were measured. Their results are shown in these three graphs. Note that only sweating rate was measured after each bout of exercise. Body temperature was measured after the first two bouts of exercise, and blood solutes after only the first bout of exercise.
Source: Adapted from Sawka, M. N., Young, A. J., Francesconi, R. P., Muza, S. R., & Pandolf, K. B. (1985) . Thermoregulatory and blood responses during exercise at graded hypohydration levels. J Appl Physiol, 59, 1394-1402.
-Which of the following homeostatic mechanisms is demonstrated in the graph of blood solutes?

A) At low percent dehydration, the addition of aquaporin proteins in the collecting ducts can maintain blood solute concentrations.
B) At low percent dehydration, the reduction of aquaporin proteins in the collecting ducts can maintain blood solute concentrations.
C) At high percent dehydration, the addition of aquaporin proteins in the collecting ducts can increase blood solute concentrations.
D) At high percent dehydration, the reduction of aquaporin proteins in the collecting ducts can reduce blood solute concentrations.