3B - Selye's General Adaptation syndrome (GAS)

Generalm Adaptation Syndrome (GAS)

A three-stage physiological response to stress that occurs regardless of the stressor that is encountered. 

• Alarm reaction (Shock & Countershock)

• Resistance 

• Exhaustion 

GAS graph

Alarm Reaction

Occurs when the person or animal first becomes aware of the stressor. 

• Defensive reaction creating tension and alertness as well as readiness to respond to the stressor. 

Shock (alarm)

• Ability to deal with the stressor falls below normal level 

• Body reacts as if injured: BP and Temperature drop below normal, loss of muscle tone 

• PARASYMPATHETIC NS ACTIVATION 

• cortisol is not released yet, as body is not ready to deal with the stressor

Countershock (Alarm)

Sympathetic NS - FFF response occurs 

• adrenaline, noredrenaline and cortisol are released 

• Body's resistance to the stressor increases 

• Organism becomes highly aroused and alert in preparation to deal with the stressor. 

• Increase in heart rate, breathing rate and blood glucose levels

Resistance

Body's resistance to the stressor rises above normal 

• Intense arousal of stage 1 decreases, but physiological arousal remains above normal. 

• Unnecessary physiological processes are shut down to save energy (digestion, growth, sex drive, menstration) 

• Cortisol continues to be released into the bloodstream 

• If present for a long time, immune system becomes supressed (Increases susceptability to developing illness) 

• Ability to deal with the initial stressor increases, But resistance to other stressors may decline. 

Exhaustion

The body cannot maintain resistance and cannot deal with the stressor. 

• Body's resources are depleted (lowered cortisol) as it has been dealing with the stressor for a prolonged time. 

• Resistance to disease is weak (from high cortisol levels in bloodstream), more vulnerable to physical and mental illness, Wear and tear. 

• Symptoms: extreme fatigue, high levels of anxiety, symptoms of depression, nightmares, impaired sexual performance, hypertension, gastrointestinal problems and heart disease.

Strengths of the GAS model

• Recognises a predictable pattern of physiological responses associated with distinct stages and substages, which can be measured in individuals.

• Recognises the relationship between chronic stress and illness.

• Provides objective, empirical information about the biological processes (e.g. hormone secretion) involved in the stress response.

Limitations of the GAS model

• A ‘one size fits all’ model; fails to recognise the subjective nature of the stress response and therefore doesn’t take into account how different people respond to stressors.

• Only focuses on the biological aspects of stress. It ignores the importance of psychological factors, including emotion and cognition (interpretation), in the stress response.

• Based on research that was conducted on rats, reducing the generalisability of the model to the human population.