General Adaptation Syndrome (GAS)
- Selye (1956) developed the GAS model of stress, arguing the physiological effect of stressors was to leave humans and animals vulnerable to illness
- Selye developed his model after measuring the effects of stress on rats suffering various stressful conditions, such as extreme cold, electric shocks and invasive surgery, and generalising the findings to humans
- The GAS model comprises three stages:
Stage 1 - Alarm |
Stimulated by the hypothalamus, the autonomic nervous system (ANS) releases adrenaline and noradrenaline (stress hormones) into the bloodstream: heart rate and blood pressure both increase in a fight or flight response |
Stage 2 - Resistance |
If the stressor continues, the fight-or-flight response ceases but stress hormone output from the adrenal cortex continues and the adrenal glands may become enlarged |
Stage 3 - Exhaustion |
If the stressor continues for a long time, the body’s resources are reduced,the immune system may be damaged and stress-related diseases such as high blood pressure and cardiovascular disorders are likely to occur |