General mechanisms of the effect of weightlessness on the human body.

Publisher Summary This chapter analyzes the mechanisms of the adaptation of the human body to microgravity, a process which leads to a redistribution of the functional load on the various systems and regulatory mechanisms. It thus leads to the establishment of a new level of functioning and homeostatic regulation of the body's primary physiological systems. Stabilization of this level is achieved through the mobilization of immediate and delayed adaptive responses, and the formation of new or reinforcement of existing functional systems at the expense of increased power and hyperfunction of the structures involved in these systems. Decrease of the functional load, as on the musculoskeletal system, during prolonged stay in microgravity leads to de-adaptation processes, like the reversible bone demineralization followed by an impairment of some functions and an activation of regulatory mechanisms.

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