[Effect of weightlessness on human cardiovascular system]

During the space flight the cosmonaut is exposed to many stressogenic factors. The science is especially interested in microgravitation as an environmental element affecting the life of the crew in a cosmic vehicle, which is in contrast with human physiology in terrestrial conditions. The space medicine is interested to establish whether microgravitation has a harmful effect on the human organism. The answer is given in many biological studies. These studies concerne the microorganisms, insects, fishes, monkeys, cells, plants, seeds and humans. On the basis of these investigations, it was established that microgravitation had no effect on the genetic process, embryogenesis, DNK, RNK synthesis and other amino-acids. These results contributed to a longer stay of the man under the condition of microgravitation. The term weightlessness used in this paper is identical with the term microgravitation. On the basis of medical investigations, it was established that microgravitation provoked a spontaneous adaptation of the human biological system. The paper deals with the influence of microgravitation on the cardiovascular system. The diagrams show the results of the studied parameters in 160 cosmonauts, who lived several months under the influence of microgravitation. The adaptation and readaptation are expressed as the function of time. During microgravitation the new homeostasis was achieved after 45 days, and the readaptation to earth gravitation conditions after about 90 days. Thus, the behaviour of the cardiovascular system depends on the use of prophylactic measures during and after the flight. The use of prophylactic measures slow down the process of spontaneous adaptation to microgravitation, and accelerate the readaptation to terrestrial gravitation. However, the prophylactic measures cannot annul the influence of microgravitation on the cardiovascular system and on other biological systems. This annulment would be possible if the future space vehicles would be supplied with the artificial gravitation of 0.3 g. The study of human adaptation to microgravitation is important from theoretical and applied aspects in space medicine. The space medicine is one of the important factors for the security of the prolonged human stay in conditions of microgravitation.