It has been clear for sometime that when humans go into space, many changes occur in their physiology. Several studies have also indicated that basic biological processes are altered in microgravity. It is not likely that the processes are separable.
Human physiology is predicated on the homeostatic functioning of organs that are composed of cells.
All of these complex functioning systems have evolved in the presence of gravity, and when exposed to microgravity, they are forced to function in a new and novel environment. Thus, in attempting to understand the adaptation to microgravity, scientists are forced to evaluate not only the clinical manifestations of an organismal response to the new environment but also the underlying cellular and organ response. This requires an integrated approach that includes both basic research as well as the more operational aspects of clinical research. One approach to understanding adaptation to microgravity involves empirical research in which humans or appropriate animal models are subjected to the space environment for prolonged periods and are monitored continuously for signs of changes. A more appropriate research strategy is to study basic mechanisms and, based on the knowledge acquired, to design appropriate countermeasures.