Chapter 9 – Stress
Even if you know the physical effects of stress, you may be unaware of the different stages of stress, known as the general adaptation syndrome (GAS). The general adaptation syndrome is a universal and predictable response pattern to all stressors, whether good stress (called eustress) or bad stress (called distress).
Endocrinologist Hans Selye first described GAS in the 1930s and 1940s. He believed that when we are chronically exposed to stress, over time, the stress response causes aging and disease. During experiments with rats, Selye observed a series of physiological changes in the rats after they were exposed to stressful events.
After additional research, Selye concluded that these changes were not an isolated case, but rather the typical response to stress. He subsequently identified these stages as alarm, resistance, and exhaustion. Understanding these different responses and how they relate to each other may help you cope with stress. The sequence of physical responses associated with GAS is the same for eustress and distress and occurs in three stages.
Three Stages of GAS
1. Alarm reaction stage
In this stage, your body experiences the “fight or flight” response. This natural reaction prepares you to either flee or protect yourself in dangerous situations. The sympathetic branch of the autonomic nervous system is activated and the adrenal glands secrete two hormones to stimulate your reactions to stress: epinephrine (also known as adrenalin) and norepinephrine (also known as noradrenalin).
Adrenalin mobilizes glucose and fatty acid release from fatty cells. The body is able to use both as energy to respond to stress. Adrenalin and noradrenalin also have powerful effects on the heart. Both the heart rate and stroke volume are increased, thereby increasing the body’s cardiac output. They also help to shunt blood away from the other parts of the body and thereby push more blood to the heart, brain, and muscles as the body prepares to attack or flee. At the same time, the adrenal glands also release cortisol, to help meet the body’s energy needs in times of stress.
2. Resistance stage
After the initial reaction to the stressor during the alarm reaction stage, the parasympathetic branch of the autonomic nervous system counteracts the changes that the stressful stimulus has produced, and attempts to restore a state of homeostasis, the default state in which the body functions normally.
During the resistance stage, the results of the hormonal changes which occurred in the previous stage are still apparent, including increased glucose levels in the blood and higher blood pressure, but stress hormone levels begin to return to normal, enabling the body’s focus to shift from alertness to repair.
If the resistance stage continues for too long the body will stay in a state of alertness and continue to produce the stress hormones. Signs of the resistance stage include:
- Irritability
- Frustration
- Poor concentration
3. Exhaustio