APA Dictionary of Psychology

the parts of the central and peripheral nervous systems responsible for the synthesis and actions of norepinephrine (noradrenaline). The system has roles in cognitive functioning, sleep, nociception (pain perception), physiological arousal, and emotions. It is sensitive to chronic stress, which may alter the synthesis, storage, and release of norepinephrine; such alterations are believed to contribute to posttraumatic stress disorder, substance abuse, and anxiety, but the exact mechanisms are not fully understood. Compare adrenergic system.