The Neurobiology of Stress

Stressors represent a potential threat to the individual human or animal, and the stress response is integral to adapting to the stressor. The identification of a stimulus or collection of stimuli as a stressor depends upon perception of the intrinsic properties of the stimuli, learned and unlearned factors, as well as the animal's early experiences and status. The activation of the stress response is mediated by a hierarchical system involving cortical, limbic, and brain-stem structures. The response involves the simultaneous activation of the hypothalamopituitary–adrenal response and the sympathetic nervous system, together with the sympathoadrenal system. Coordinated outputs from these ensure the appropriate channeling of resources to adapt to the stressor. The response impinges on other systems, including the reproductive system, growth, and nociception. Rapid termination of the response is necessary to prevent deleterious effects of sustained activation, including somatic, cognitive, and psychological dysfunction.