general adaptation syndrome

n. (GAS) A description of response to chronic stress in three stages: alarm, resistance, and exhaustion. In the first stage of response to stress, the body first goes into shock, in which body temperature, blood pressure, tissue water level, and muscle tone drop, and then into arousal or countershock, in which there is arousal of the sympathetic nervous system into its flight-or-fight stance. The second stage is becoming subjectively accustomed to the elevated blood pressure and hormone levels and decreased digestive and immune function characteristic of sympathetic arousal. These changes can lead to organ damage if arousal continues chronically. In the exhaustion stage there is a breakdown of function characterized by sleep disturbance, restlessness, irritability, anxiety, crying fits, depression, loss of concentration, becoming easily startled, disturbed coordination, and tremor. The probability of illness is significantly raised after prolonged stress.