by Diverse Nocuous Agents in Nature. His concepts have been utilized in medicine and in almost all biological sciences from endocrinology to animal breeding and to social psychology.
Selye described the alarm reaction as having three stages: the alarm reaction, when the body detects the external stimulus; the adaptation stage, when they body engages defensive countermeasures against the stressor; and the exhaustion phase, when the body begins to run out of defenses (Stress). Stress includes eustress, the effect of positive events, and distress, the result of negative events. It can contribute directly and indirectly to disorders of both the body and the mind.
In the second phase, ideally the body learns to cope with the stressor, and this stage continues until the stressful situation is resolved, leading to a rapid return to the normal state (Adaoptogens; Dean). However, the capacity to adapt varies from person to person, and what is stimulating and exciting to one person may be devastating to another. In the exhaustion phase, the powers of adaptation are lost and disease results. This third stage is sometimes referred to as the adrenal maladaptation stage, or hyperadaptosis, and adrenal dysfunction may occur. The normal balance in secretion of hormones and releasing factors may be disrupted, and the hypothalamic-pituitary-adrenal axis may malfunction.
Another important finding of Selye was that the stress response by the body is the same, no matter what the source of the stress (The principles). Selye's experiments on rats showed that when he used different stressors such as heat, cold, trauma, infection, fear, hemorrhage, and the injection of noxious substances, they all produced the same effects in the animals. All had swollen and hyperactive adrenal glands, shrunken immune systems (thymus gland and lymph nodes), and gastrointestinal ulcers. His animal model replicated what he found in humans who were
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