Astronauts who spend significant time at zero gravity often become somewhat anemic upon return to Earth. One way to compensate for the process that leads to this anemia might be to supply the astronauts with ________ during the mission in space
a. a diet higher in protein and iron
b. a diuretic, which will cause them to excrete more fluid
c. a growth factor that leads to increased red blood cell production
d. higher levels of oxygen in the shuttle atmosphere
e. more opportunities to rest or sleep
C; The anemia results from a two-stage process: First the body loses fluid in response to the vascular changes brought about by microgravity. Then the bone marrow reduces the production of red blood cells because the remaining cells are now more concentrated, since the same number of cells occupies a smaller volume of plasma. Upon return to Earth the blood volume increases back to normal levels, diluting the red blood cells. The correct answer choice suggests that the problem be treated by maintaining the correct total number of red blood cells throughout the mission. A diuretic would make things worse.
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