Since the seventeenth century, the concept of stress has undergone much change. Initially, attempts were made to identify it with exogenous or endogenous stimulants to which an animal organism reacted.' Later, attempts were made to identify it with the organism's response to it. According to Selye, stress was considered an aspecific response of an organism to a request or stimulant. From this definition of stress, we began to identify, on the one hand, the heterogeneity of stimulants, which can be external or internal to the organism (physical, chemical, acoustic, somatic, psychic, intrapsychic, psychosocial-cultural, etc.) and, on the other, the individual response identified and described in different ways by several authors, noting the variable participation of three basic systems: neurovegetative, neuroendocrine, and immune.* These systems interact with one another, being integrated with the brain. The psychological modifications that we see in response to stress, the main aim of which is to maintain homeostasis and corporeal integrity, have been the subject of studies that are now considered a new discipline, psychoneuroendocrinoimmunology. The studies of Cannon and Selye in the 1930s in which sympathetic system and suprarenal involvement into adaptative reactions of the organism to stress were shown for the first time formed the basis for the study of the connections between the nervous and endocrine systems. Subsequently, in the 1970s, Mason's studies and then those of Bahnson showed the existence of an emotional response to stress determined by activation of the hypothalamus-hypophysis-cortex suprarenal (H-H-Cs), which allowed a series of vegetative activities concerning several apparatuses, the cardiovascular one as well, and activation of several metabolisms, to handle the immediate requests caused by stress; the behaviors predispose and prepare the organism's motor activity to neutralize the stress event. This response in man is filtered at the knowledge level, expressing itself through many different kinds of behavior, including facial miming, speech, movements that are filled with intrapsychic experience of each individual such as rage, depression, and anxiety. Basically all of this is possible because of the philogenetic acquisition of the new cortex, allowing the acquisition of knowledge and the rationalization of the exterior world, so that man elaborates the response to stress first at the knowledge level (neocortex and behavior answers) and then at the emotional level (limbic, neuroendocrine, and neurovegetative systems). Intrapsychic anxiety engendered under cortex structures may influence the knowledge sphere, and individuals facing stress may prefer a biologic reaction or a psycho-
