There is no life without stress and without adaptation to stress there is no life. Adaptation to stress requires the intervention of the nervous system for proper coordination and adjustment of the intensity of the response to stressful stimuli (stressors). The sympathetic nervous system is primarily responsible for rapid adaptive responses to stress, of which the classic example is the “fight or flight” response. This response is mediated by adrenaline secreted from the adrenal medulla and noradrenaline released both from the adrenal medulla and postganglionic sympathetic neurons. However, inadequate sympathetic activation, both in duration and intensity, may be at the origin of several “stress-related” diseases (hypertension, heart failure, pain, etc.). Although the sympathetic nervous system has traditionally been viewed as a one functional unit, the idea of a differentiated contribution to the stress response between the adrenal medulla and the sympathetic neurons, also with differentiated pathophysiological implications, is gradually gaining ground. Keywords: stress; sympathetic nervous system; adrenal medulla; chromaffin cell; stress-related diseases