[Evolution of the stress concept].

New aspects of the classical Selye stress theory are considered. Stress is interpreted as a systemic response of the organism. In the last years the stress concept h as undergone transformation to the notion of emotional stress. In the context of the theory of functional systems, emotional stress is regarded as developing in the so-called conflict situations in which the participating subjects are unable to achieve useful adaptive goals. The primary cerebral mechanisms of emotional stress and the role played by neuromediators and neuropeptides are discussed. Dynamics of impairment of various functional systems under stressful conditions is discussed with special emphasis on individual tolerance to emotional stress and the role of oligopeptides (substance P), delta sleep inducing peptide, beta-endorphin and semax as antistress factors increasing resistance to stressful impacts.