2.8 General Adaptation Syndrome: Stages, Definition & Examples
General Adaptation Syndrome Defined
Think about a time you were stressed. What did it feel like? How did you know you were stressed? You probably remember your heart rate increasing. If you were stressed long enough, you may have felt tired and even gotten sick. Hans Selye described three predictable stages the body uses to respond to stressors, called general adaptation syndrome (GAS). The first stage is the alarm stage, which provides a burst of energy. In the second stage, known as the resistance stage, the body attempts to resist or adapt to the stressor. The last stage is known as the exhaustion stage because energy is depleted.
Stages of General Adaptation Syndrome
During the alarm stage, the body responds to the distress signal sent to the hypothalamus with a burst of energy to help deal with the stressor. If you were walking at night and something jumped out from behind a tree, your hypothalamus would tell the pituitary gland to release glucocorticoids, which are hormones. In response, the adrenal glands release cortisol and adrenaline to help the body react. In addition to an increase in heart rate and breathing rate, blood glucose levels increase to boost energy.
Once your body initially responded to the stress of whatever jumped out from behind the tree, it will continue to maintain a level or alertness to help fight or adapt to the stressor. This is called the resistance stage. The adrenal cortex continues to release glucocorticoids to help the body react to the stressor until the stress is resolved or the body can no longer resist. Deep energy reserves are used until the stressor is resolved or reserves are depleted. Because the body’s energies are going to the stressor, the body is not able to fight off colds and flu during this time.
If the stress continues long enough or intensely enough without resolution, exhaustion will set in when energy is depleted. Chronic stress increases the chance of illness even if it does not progress to the exhaustion stage. During the exhaustion stage, the body shuts down and cannot respond. The body is too weak to resist illness, muscles are weak, and blood pressure is high. Long-term stress can damage the hippocampus. The individual cannot function. Ignored, exhaustion can lead to illness and death.
Example of General Adaptation Syndrome
When something jumps out from behind a tree when you are walking at night, you are startled (alarm stage) and turn around and run as fast as you can towards your home (resistance). Once you arrive to your home, you realize you are breathing fast, your heart is beating very quickly, and you don’t think you could have made it any further if you had to because your legs are weak (exhaustion). Once home, your heart rate and breathing return to normal.
In the event of a non-physical threat, such as stress from work or school, the stages are the same, but the body does not have an opportunity to work off the stress through physical exercise. Stress impacts your health by creating physical responses due to the body’s natural response to stress.
You should have the ability to do the following after watching this video lesson:
- Define general adaptation syndrome and identify who is credited with its description
- Describe the three stages of general adaptation syndrome
- Explain the effects of non-physical stress and chronic stress on the body