Saturday, May 05, 2012
"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. 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."
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