Stress and the Brain

Stress and the Brain

Stress and the Brain

Stress and the Brain

Synopsis

This volume in the series focuses on issues related to stress and the brain. Although stress affects many other aspects of physiology, they are beyond the scope of this volume. The volume begins with a seminal work by Selye describing the stress response, an adaptive response that permits an organism not only to survive but also to cope with the stressor. Further research established that this general adaptation system involved several “limbs.”

Excerpt

An increasingly compelling body of data is demonstrating that stress exerts significant effects on brain function and on general health. Despite the advances detailed in the papers included in this volume, the term “stress” continues to have many imprecise meanings in popular culture and in medicine. Thus it is important to start with definitions. Stress can be defined as an environmental, physiological, or psychosocial challenge that is interpreted by the brain as excessive or threatening. One difficulty for the scientific investigation of stress is that the same challenge may be experienced by different people, or by different animals in the laboratory, as very stressful, less stressful, or not at all stressful. A useful approach is to focus on the physiological and behavioral responses to a challenge rather than on the challenge itself. Thus the serious study of stress began in the 1930s when Hans Selye recognized that diverse threats and demands on an individual led to a generalized response that he referred to as “general adaptation syndrome.” Observing the responses that followed the brain’s appraisal of a stimulus as stressful permitted the definition of a stress response.

First the stress response activates the sympathetic nervous system, that part of the autonomic nervous system (thera by nerves, the sympathetic nervous system directs the adrenal medulla to release epinephrine (adrenaline). Overall, sympathetic activation leads to increased heart rate, blood pressure, and respiratory rate and redirects the blood supply to voluntary muscles.

A second limb of the stress response leads to the release of stress hormones from the endocrine system; because this response is initiated by a structure at the base of the brain called the hypothalamus, it is called the neuroendocrine response to stress (Habib et al., 2001; Habib et al., 2000). A specific region of the hypothalamus, the paraventricular nucleus, elaborates the key hormone in this stress hormone cascade, corticotropin releasing factor (CRF), also known as corticotropin releasing hormone (CRH), in response to signals from higher brain centers. Important signals come from emotion-processing regions of . . .

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