Physiologist Walter Cannon first described the stress response. Cannon called this the fight-or-flight response.
Endocrinologist Hans Selye was able to specify the changes in the body's physiology that resulted from stress.
Selye found rats that he stressed developed substantial enlargement of the adrenal cortex; shrinkage of the thymus, spleen, lymph nodes, and other lymphatic structures; a disappearance of the eosinophil cells; and bleeding ulcers in the lining of the stomach and duodenum.
Selye summarized stress reactivity as a three-phase process: alarm reaction, stage of resistance, and stage of exhaustion. He defined stress as the nonspecific response of the body to any demand made upon it.
Cardiologist Herbert Benson studied transcendental meditation and developed a similar meditative technique that he successfully employed to help reduce his patients' levels of high blood pressure.
A stressor is a stimulus with the potential of triggering the fight-or-flight response. Stressors can be biological, psychological, sociological, or philosophical in origin.
The longer one's physiology varies from its baseline measures (duration) and the greater the variance (degree), the more likely one is to experience ill effects from stress reactivity.
Stress has been defined differently by different experts. Some define stress as the stimulus, others as the response, and still others as the whole spectrum of interacting factors. This book defines stress as the combination of a stressor and stress reactivity.
