[Analysis of mechanisms regulating the heart in extreme situations].

Parasympathetic influences on functional and structural condition of myocardium in the process of stress modelling and adrenaline action on the background of the blockade of M-cholinoreceptors, was studied in 124 white rats. The stress was caused by means of severe exteroceptive stimulation or immobilization. Adrenaline and stress conditions caused impairment of automatism, change of conduct rate in the heart muscle and of force of excitement, anisotropia of muscle fibers, and penetration into the heart muscle cells of fluorescine. The effects were accelerated by diminishing of parasympathetic influences. The immobilization stress increased parasympathetic cardiac reflexes.