A fall in plasma sodium concentration

A. True   Due to excessive reabsorption of water from the collecting ducts of the nephron.

B. False   Water is drawn into cells from the hypotonic extracellular fluid; water intoxication may occur.

C. True   People sweating heavily may replace their water, but not their salt, deficit; they tend to get muscle cramps unless they supplement their salt intake.

D. True  Sodium ions are responsible for nearly half of plasma osmolality.

E. False   The hypothalamic osmoreceptors responsible for thirst respond to hypertonicity, not hypotonicity of the ECF