RESUMO
The article discusses the problems of the process of environmental adaptations appearance which are based on the general principles of functional systems' constitution. The value of the theory of functional systems development as the basis for physiological cybernetics (P. Anokhin, 1935) is also given. A general adaptation syndrome ("a stress - syndrome") that was discovered by H. Selye is chosen as an example to explain the development of the stages of the functional system of the stress, the sequence and value of ongoing physiological reactions and negative feedback interactions. The stress - syndrome reactions are the nonspecific response of a particular organism to various factors: emotional shock, trauma, infections, surgery, burns etc. The article also paid attention to the reasons and conditions for the failure of adaptations' emergence and the transformation of adaptive reactions into pathological ones. The key role of stress syndrome reactions as the main or auxiliary etiological factor in the development of coronary heart disease, hypertension, atherosclerosis, lesions of the stomach and duodenum, immunodeficiencies, etc. is indicated. To be effective in interactions with the environment, organisms have developed different mechanisms which are not only activating but also suppressing the excessive activity of the functional stress system that damages the organs. Therefore, the article considers the significance of negative feedback adaptations that act as stress - initiating and stress - limiting mechanisms.
