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Medicine LibreTexts

3.5: General Adaption Syndrome

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  • Selye's Concept of General Adaptation Syndrome

    Hans Selye (1907-1982) started the modern era of research into something called stress. In 1950, Selye addressed the American Psychological Association convention. He described a theory of stress-induced responses that become the standard model of stress, the one people usually refer to (or criticize) in academic journal articles about stress.

    How did Selye discover the stress response?

    Selye's discovery of the stress response was an accident. He was doing research on the effect of hormone injections in rats. Initially he thought he detected a harmful effect from the hormones, because many of the rats became sick after receiving the injections. But when Selye used a control group of rats, injected only with a neutral solution containing no hormones, he observed that they became sick, too.

    As it turned out, the rats responded more profoundly to the trauma of being injected than they did to the hormones. The experience of being handled and injected led to high levels of sympathetic nervous system arousal and eventually to health problems such as ulcers. (Note that stress was not found to directly cause ulcers by Selye.) Selye coined the term "stressor" to label a stimulus that had this effect.

    What is a stressor for rats? For lab assistants?

    The immediate response to stress is the release of adrenaline into the blood plasma (the liquid part of the bloodstream). "Mild stressors such as opening a cage door or handling a rat produces an eightfold increase in plasma epinephrine [adrenaline] concentrations" (Axelrod and Reisine, 1984). The sentence is ambiguous; does the rat or the human experience the eightfold increase in adrenaline? In this case, it is the rat which is having its adrenaline (plasma epinephrine) measured. However, many lab assistants probably experience a burst of adrenaline, too, when handling a rat for the first time.

    What were the three stages of Selye's General Adaptation Syndrome?

    Selye proposed a three-stage pattern of response to stress that he called the General Adaptation Syndrome (GAS) . He proposed that when the organism first encountered stress, in the form of novelty or threat, it responded with an alarm reaction. This is followed by a recovery or resistance stage during which the organism repairs itself and stores energy. If the stress-causing events continue, exhaustion sets in. This third stage is what became known popularly as burn-out. Classic symptoms of burn-out include loss of drive, emotional flatness, and (in humans) dulling of responsiveness to the needs of others.

    Hans Selye’s Study of Stress Response

    In 1934, Hans Selye at McGill University discovered a new type of hormone. He gave rats daily injections of ovarian extract and found that the rats had enlarged adrenals and shrunken spleens, thymus, lymph nodes, and intestinal ulcers. “Multiple organs in the body generate this hormone, and thus he announced that it is a nonspecific response of body to noxious agents. (Evan-Martin, 2007)

    In 1936, Selye defined these series of symptoms in the experiments with the rats as the General Adaptation Syndrome, which consists of three stages: the alarm stage, the resistance stage, and the exhaustion stage (Evan-Martin, 2007). The alarm stage is similar to the fight-to-flight response, and the body mobilizes resources to react to the incoming noxious agent. The resistance forces will be built up when the noxious challenge is detected as continuing. The exhaustion stage will cause death if the body is unable to overcome the threat.

    For example, your mom told you that you are going to take the SAT next month. The first reaction is shock, starting complaints and feelings of stress, which represent the beginning of the first stage. In the resistance stage, you will try your best to do practice tests, reviewing vocabulary, studying any type of study aids that are available. Finally, you will feel like you are doomed to fail this test and feel desperate, feel constantly anxious, have difficulty falling asleep and waking up in the morning. The exhaustion of this stage will have deleterious effects on your health by depleting your body resources which are crucial for the maintenance of normal functions. Your immune system will be exhausted and function will be impaired. Also, the decomposition which is a functional deterioration of body may happen as the exhaustion stage extends. Selye believed that one becomes sick at that point because stored hormones secrete during the stress response are depleted (Sapolsky, 1998).