GRAVITATIONAL FACTOR AS A BASE OF THE EVOLUTIONARY ADAPTATION OF ANIMAL ORGANISMS TO ACTIVITIES IN THEEARTH CONDITIONS
Authors:   Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow, Vinogradova O.L. , Tomilovskaya E.S. ,   Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow, Kozlovskaya I.B. ,   Institute of Biomedical Problems of the Russian Academy of Sciences, Moscow
Published: December 2020

A review of the currently available ideas about the role of gravitational factor in the activity of the sensorimotor and cardiovascular systems, as well as new fundamental problems and questions for space medicine and physiology, is presented. The review presents data on the embryogenesis of animals under conditions of weightlessness, the evolution of the motor and cardiovascular systems and the peculiarities of their functioning under conditions of gravity, as well as in the change of gravitational load. Much attention is paid to the results of unique studies in modeling gravitational unloading on Earth: antiorthostatic hypokinesia, dry immersion and suspension, which made it possible to study the mechanisms of regulation of various body systems under conditions of altered gravity. Terrestrial organisms have learned to function in the gravitational field. Almost all systems of their body are gravitationally dependent. However, the extent and mechanisms of this dependence have long remained unclear. Space flights have opened up the possibility of studying the activity of living systems in the absence of gravity. Among the factors mediating the effect of weightlessness on the motor system, changes in the activity of sensory systems occupy an important place. Under the Earth conditions, the afferent support of motion control systems is polyreceptive: this is vision, and the vestibular apparatus, supporting and muscular afferentations. In zero gravity, the activity of some channels is completely eliminated (support afferentation), others are distorted (vestibular apparatus), and still others are weakened (proprioception). Similar processes occur in the cardiovascular system: with the loss of the pressure gradient caused by gravity, profound changes occur in the structure and functioning of the heart and vessels, both resistive and capacitive. The question of how much the various changes occurring in the cardiovascular system are associated with the disappearance of the gravitationally dependent pressure gradient is still open. It is not possible to solve all the problems of gravitational physiology In space flights. Therefore, various methods have been developed for simulating gravitational unloading on Earth. New data on the mechanisms of changes occurring in the sensorimotor system were obtained by comparing flight data and data obtained in model experiments. The fundamental problem for the gravitational physiology of cardiovascular system is the degree of correspondence of the changes observed in laboratory animals and under model conditions (antiorthostatic hypokinesia, immersion, suspension) with the changes that are recorded in real space flight in humans. This problem is specially discussed in the review. At the same time, in the light of the upcoming interplanetary expeditions, many questions remain unresolved, in particular, the problems of post-flight readaptation of the motor and cardiovascular systems to gravity conditions. This is a fight against loss of strength, endurance, orthostatic instability. The development and improvement of a system for preventing the negative effects of space flight factors is impossible without understanding the mechanisms of development of the observed changes.