[简答题] SURVIVING IN SPACE Motion sickness troubles more than two-thirds of all astronauts upon reaching orbit, even veteran test pilots who have never been airsick. Though everyone recovers after a few days in space, body systems continue to change. Deprived(丧失) of gravity information, a confused brain creates visual illusions. Body fluids surge to chest and head. The heart enlarges slightly, as do other organs. Sensing too much fluid, the body begins to discharge it, including calcium, electrolytes (解液) and blood plasma (血浆). The production of red blood ceils decreases, rendering astronauts slightly anaemic (贫血的). With the loss of fluid, legs shrink. Spinal (脊骨的) discs expand, and so does the astronaut--who may gain five centimeters and suffer backache. Though the .process may sound terrible, astronauts adjust to k, come to enjoy it and seem no worse for wear-at least for short missions such as space shuttle flights that last a week or two.

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