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Capacities of the Human Organism: Defense Mechanisms and Adaptations in Conditions of Maximum Overload and the State of Weightlessness
- Perspectives in Biology and Medicine
- Johns Hopkins University Press
- Volume 5, Number 4, Summer 1962
- pp. 527-533
- 10.1353/pbm.1962.0016
- Article
- Additional Information
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CAPACITIES OF THE HUMAN ORGANISM: DEFENSE MECHANISMS AND ADAPTATIONS IN CONDITIONS OF MAXIMUM OVERLOAD AND THE STATE OF WEIGHTLESSNESS VASILY PARIN* The factors involved in human space flight and penetration into outer space that should be taken into account can be divided into three groups. The first group includes extremely low barometric pressure, absence ofmolecular oxygen, ionizing radiation (cosmic, ultraviolet, and corpuscular radiation), unusual temperature conditions, presence ofmeteorite substance , etc. This group has to do with the physical state in outer space. The second group of factors is connected with the flight of a rocket vehicle and includes noise, vibrations, accelerations, and weightlessness. The third group encompasses the conditions oflife in a space ship and the safety devices for the crew (airtight cabins, space suits, etc.). Included here are the effects ofthe space ship's artificial atmosphere, the peculiarities ofnutrition, a specific regimen ofwork and rest, insulation, a sharp reduction in outer stimulation, limitation of movement, emotional strain, the inconvenience ofbeing restricted by the safety devices, etc. Most important for the biologist and physician are all the aspects ofthe problem of flight safety: protecting man and the living organisms that may possibly travel with him from the harmful influence of space flight. Naturally, the solution of this problem is connected, first of all, with the fullest possible assessment ofthe conditions and factors which influence the vital activities ofthe human organism and present a real or potential danger to it. It is quite possible that future investigations of outer space and biological experiments will reveal some additional conditions which we do not recognize yet; or perhaps conditions to which we have not attached due importance. In this connection it is worth noting that solution * Member, U.S.S.R. Academy ofMedical Sciences. Address: % Press Department, Embassy of, the U.S.S.R., 1706 Eighteenth Street, N.W., Wajhington 9, D.C. 527 ofbiological problems depends in great measure on the general progress ofspace research. Accumulated experience as well as special experiments on animals and man have contributed to our knowledge of the possible physiological (biological) effects and the permissible limits ofthe force and/or duration ofthis or that factor or set offactors. As some potentially harmful effect is recognized, methods are sought for raising the resistance ofthe human organism—either by developing natural compensatory mechanisms, or by applying appropriate protective devices. Ofcourse, the desire, natural for a physiologist, to exclude the unfavorable factors ofspace flight on man is limited by difficulties. Therefore, sensible compromises must be found between some definite necessities ofa living organism and the possibilities offered by a space ship. A large series ofexperiments has shown that the most serious problems of space flight, which should be dealt with first of all, are acceleration, weightlessness, space radiation, and emotional tension, which factors affect a living organism at different stages offlight. During the boosting ofthe rocket system and the re-entry ofthe space ship into the denselayers oftheatmosphere, the strongest effects resultfrom acceleration accompanied by a substantial emotional strain. The influence varies according to the direction ofthe force. When the acceleration force affects man in the feet-to-head direction, he can stand six to eight times the force of gravity for a very short period oftime—0.3 second. When the force affects the body in the head-to-feet direction, man is capable of standing, for the same period oftime,only twice the force ofgravity. As the force increases, the time during which man is able to withstand it decreases considerably. The human organism is least affected when the acceleration acts in the direction perpendicular to the longitudinal axis of the body—known as transverse acceleration, However, this force may cause disorders in respiration , hemodynamics, and nervous regulation which can become critical when the degree and duration ofacceleration reach a certain level. Most investigators are ofthe opinion that disorders ofgas exchange in the lungs contribute substantially to the malfunction. The undermining of compensatory mechanisms leads to a critical state of the organism, which is manifest in a sharp decrease ofworking capacity and a subsequent breakdown ofvital functions. 528 Vastly Parin · Adaptations to Overload and Weightlessness Perspectives in Biology and Medicine · Summer 1962 It is important to find out...