How Does Your Body React to Stress?
When we perceive external events as stressors, our body goes through a complex sequence of reactions to prepare us to cope with the stressors. This sequence was investigated in a number of animal experiments between 1930 and 1960. On the basis of these studies, physiologist Hans Selye proposed a theory to explain the body's reactions to stressors.
Drawing on ideas proposed by Walter Cannon, Selye argued that every organism has a state of internal balance called homeostasis. External stressors disturb this balance, producing an immediate general physiological arousal. The organism adjusts to the stress in stages, first mobilizing its resources, then using them to cope with the stress, and eventually depleting its energy resources. Selye called this sequence of body reactions the general adaptation syndrome. When the stressor occurs -- for example, when you hear footsteps behind you in a deserted alley -- your body briefly goes into shock. It then mobilizes its resources to preserve homeostasis against your reaction to the stressor. If the stressor continues for a while, those resources will be reduced and eventually exhausted.