General Adaptation Syndrome
A profound physiological reaction of an organism to severe stress, consisting of three stages.
The first stage of the general adaptation syndrome is alarm reaction, and includes the shock phase and the countershock phase. In the shock phase, there are significant changes in several organic systems. For example, body temperature and blood pressure are lowered, and muscle tone is decreased. In the countershock phase, there is a defensive response to these changes, including an increased production of adrenocortical hormones. The second is resistance, during which the affected systems recover toward their normal levels of functioning. The third stage is exhaustion, and is reached if the defenses of the organism are unable to withstand the stress. In the exhaustion stage, the shock phase of the alarm reaction is essentially repeated, resulting in death.
Selye, Hans. The Stress of Life. New York: McGraw-Hill, 1978.