It has been demonstrated in chronic experiments on animals (rabbits, rats) that in the presence of a predominance of sympathetic influences on the heart during emotional stress, the disturbances that appear in metabolism and myocardial ultrastructure promote a decrease in the electrical stability of the heart, the development of disturbances in cardiac rhythm, and arterial hypertension. A predominance of parasympathetic influences on the heart during stress, to the contrary, leads to an increase in the electrical stability of the heart, and also impedes an increase in the content of catecholamines and the development of structural injuries in the myocardium. At the same time, arterial hypertension is absent. An inference is drawn regarding the adaptive-trophic, protective action of the vagus nerves on the heart during emotional stress.