What Is General Adaptation Syndrome?

Stress
The body undergoes a process called general adaptation syndrome when it responds to stress.

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General adaptation syndrome (GAS) is the process that the body undergoes when it responds to stress, whether physiological or psychological. The process consists of three stages: alarm, resistance, and exhaustion. GAS was first described by endocrinologist Hans Selye, who believed that over time, the stress response causes aging and disease when we are chronically exposed to stress.

Key Takeaways

  • The general adaptation syndrome is a three-stage process that describes how the body responds to stress.
  • In the alarm stage, the body prepares its "fight or flight" response.
  • In the stage of resistance, the body attempts to return to normal after the stress has been removed.
  • When stress is chronic, the stage of resistance can lead to the stage of exhaustion, in which the body is not able to adequately cope with stress effectively.

General Adaptation Syndrome Definition

Organisms like to maintain homeostasis, or a steady, balanced state, also known as constant internal milieu. When an organism is exposed to stress, the body uses its "fight or flight" response to compensate. General adaptation syndrome is the process that the body undergoes to attempt to return to homeostasis. Through the use of hormones, the body attempts to return to this state as soon as possible, but the system has limits. When we are exposed to chronic stress, problems and issues can result.

The Three Stages of GAS

Alarm Reaction Stage

Have you ever been in a situation where you felt stressed and your heart began to beat quickly? Perhaps you started sweating or felt like you wanted to flee? These are typical symptoms of the first stage of general adaptation syndrome, called the alarm reaction stage.

In the alarm stage, your body experiences the "fight or flight" response. When exposed to stress, our typical reactions are stimulated by two body hormones: epinephrine (also known as adrenaline) and norepinephrine (also known as noradrenaline). Epinephrine mobilizes glucose and fatty acid release from fatty cells. The body is able to use both as energy to respond to stress. Epinephrine and norepinephrine 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 to the heart, brain, and muscles as the body prepares to attack or flee.

At the same time, the body also releases glucocorticoids, particularly cortisol, to help meet the body's energy needs in times of stress. The glucocortical reaction is typically slower and of longer duration than the similar effects of epinephrine on glucose metabolism.

Stage of Resistance

When the initial threat has subsided, the body attempts to return to its homeostatic state and repair itself. This is a part of the resistance phase of the general adaptation syndrome, which is characterized by a lack of concentration and irritability. Our heart rate and cardiac output attempt to return to normal, blood pressure is reduced and the hormones secreted by the body try to go back to their prior levels. However, due to the initial stress experienced, the body remains at a heightened state of readiness for some time, in case the stress returns. Assuming that the stress is overcome, the body will return to its prior state.

However, if there is chronic stress, the body will attempt to compensate and continue in the stage of resistance. If the body undergoes stress for too long and stays in the stage of resistance, it can lead to the stage of exhaustion.

Stage of Exhaustion

The stage of exhaustion results from chronic exposure to stress. In this stage, stress is such that the body is not able to return to its original homeostatic state. In other words, the body has exhausted its internal resources and is not able to fight stress adequately. Signs of the stage of exhaustion may include anxiety and depression. The stage of exhaustion is also characterized by a compromised immune system, which makes it more difficult for the body to fight off infection. Continued chronic stress can lead to a number of related diseases and issues, such as type 2 diabetes, ulcers, and hypertension.

Sources

  • Reece, Jane B., and Neil A. Campbell. Campbell Biology. Benjamin Cummings, 2011.