Modification of Hypothalamic Neurons by Behavioral Stress

Abstract

The pituitary-adrenocortical and sympathetic-adrenomedullary systems, under neural control of select cell populations in the hypothalamus, coordinate the broad profile of adaptive bodily responses that collectively define the emergency reaction of the organism. To meet the threat of an environmental stressor, the body is initially readied for action: heart rate, blood pressure and respiration are increased, muscles function more efficiently, pain sensitivity is dampened, and a variety of other responses are coordinated in what Selye¹ termed the alarm reaction. Once the threat is reduced or identified (for all such responses display adaptation to repeated exposures to the same brief stressor), the action of these systems is self-limiting, and the body returns to normal. However, some stress situations are chronic, or recur periodically in a pattern that defeats adaptation. As a consequence of this type of malignant exposure to stress, certain bodily functions fail to return to pre-stress levels and remain in a prolonged activated state, overriding endogenous homeostatic mechanisms.