- Education and Science
Stress: Hans Selye's General Adaptation Syndrome
Hans Selye was a Canadian endocrinologist who did many experiments about the effects of stress, in particular prolonged stress.
For ethical reasons, Selye could not do his research on human participants and instead elected to do it on rats. Selye exposed these rats to stressors such as exposing them to extreme heat or cold, electric shocks, tying their legs together for around 24 hours, giving them bacterial infections and pulling their tails.
He noticed that all the different stressors he had exposed them to had the same basic physiological response: weight loss occurred, the rats developed stomach ulcers, the immune system's vital glands shrunk and the adrenal glands became enlarged.
Stage One: Alarm Reaction
In this stage, the person first becomes aware of the stressor. After becoming aware to the stressor, the body goes into a state of shock. In the state of shock, the blood pressure and body temperature drop, and temporary loss of muscle control is experienced. While in shock, the body's ability to deal with the stressor is below its normal level.
Shock is just temporary though, and is then replaced with countershock. During countershock, the animal or human becomes highly alert as it prepares to deal with the stressor. The heart and respiratory system speed up, which supplies the muscles with more energy to enable the body to either fight or run away.
Stage Two: Resistance
If the stressor is not immediately dealt with, the person or animal enters a stage of resistance, in which they try to adapt to the stressor, and cope with it. All unnecessary processes in the body, such as growth, menstruation and sex drive are shut down to save energy, so that all of it is directed towards resisting the stressor.
Hormones are released into the bloodstream, which supports resistance but damages your immune system, which messes up your body's ability to fight disease.
Stage Three: Exhaustion
If the stressor has still not been dealt with, the body enters a state of exhaustion. The person or animal can no longer deal with the effects of the stressor, and their resources are depleted. Resistance to disease is very weak, and the organism is vulnerable to physical and mental disorders.
Being in this stage for too long may cause heart disease and high blood pressure, because if the hormones (adrenalin and cortisol) released during stage two are at a high level in the body for a long amount of time, they can damage the heart and the functioning of the immune system.
Selye's General Adaptation Syndrome model has many strengths, such as the fact that it includes the idea that resources can become depleted, increasing a person's vulnerability to disease.
It also has weaknesses, the biggest being that it is a "one size fits all" model. It doesn't allow for individual differences, and ignores the fact that some people may interpret the same stressor differently (A model that does do that is the Lazarus and Folkman's transactional model of stress and coping). Critics have also argued that because most of the research the model is based on was experimenting on animals, the findings may lack relevance to humans.