The Physiology of Stress - general adaption syndrome (GAS Model) Flashcards
what are the three stages of the GAS Model
1)Alarm reaction
2)Resistance
3)Exhaustion
what is the alarm reaction stage
The threat/stressor is recognised and a response is made.
The hypothalamus triggers the production of adrenaline/noradrenaline from the adrenal glands.
The body is in ‘fight or flight’ (sympathomedullary pathway)
what is the resistance stage
The stress continues.
The body is adapting to the demands of the environment (cortisol is produced by the HPA system, elevating blood sugar and giving energy)
However, resources are gradually being depleted (i.e. biological substances manufactured in the body i.e. hormones, sugars, neurotransmitters, proteins, etc.)
While the body appears to be coping, physiologically speaking, things are deteriorating (e.g. immune system becoming less effective).
what is the exhaustion stage
The body’s systems can no longer maintain normal functioning.
Initial symptoms of the adrenaline response may reappear (absent from stage 2) e.g. sweating, raised heart rate, etc.
Adrenal glands may be damaged from previous overuse.
The immune system may not be able to cope because the production of necessary proteins has been slowed in favour of other needs.
This may result in stress-related illnesses such as ulcers, depression, cardiovascular problems and other mental and physical illnesses.
KEY STUDY: Selye (1950)
gave a variety of stressors to rats, including exposure to extreme cold and heat, intense sound or light, forced exercise and injections of various organ extracts (from cows).
A few days later Selye killed the rats and performed autopsies, finding that the stress reaction was identical, consisting of enlargement of the adrenal gland, shrinking of the thymus, spleen and lymph glands and ulcers in the stomach and small intestine.
This suggests that there is one bodily stress response, supporting the notion of the GAS.
Ethics of Selye’s research
Many believe the stress inflicted on the rats is unacceptable due to the physical harm caused (e.g. pain of being handled and jabbed with needles).
Selye thought this was justified though as he hoped it would lead to therapeutic breakthroughs in treating stress-related illnesses.
:)Selye’s GAS model was the first to explain the physiological effects of stress and influenced further research into the negative effects of stress on health.
:(However, the GAS model does not recognise the role of emotion and cognition in how a person perceives and evaluates the stressor…
Lazarus and Folkman (1984) developed the ‘transactional model’ to explain the role of cognitive appraisal in stress responses, explaining how an individual’s assessment of the demands of the situation (‘perceived demands’) and their perceived ability to cope determines the physiological response.
For example, one person might perceive an exam as a stressor and feel unable to cope with the demands placed upon them by that exam, thus activating a stress response, whilst another individual might be completely unfazed.
Selye’s failure to recognise the role of emotion and cognition in responding to stress could be explained by the fact that much of his initial research was conducted on rats.
Why might it be difficult to generalise the findings to humans? How might humans and rats differ with regard to stress responses?
Rats may not respond to stress in the same way as humans.
For example, rats are more passive in their response - whereas humans often actively try to find ways to lessen the stressor (i.e. there are cognitive elements to stress management)
Therefore, the response may not be the same/as simplistic in humans.
Selye’s GAS model fails to recognise individual differences in stress responses, as well as responses to different types of stressors:
Selye believed that individuals respond in an identical way to all stressors (i.e. the stress response is non-specific), but is the GAS really ‘general’?…
Mason (1995) replicated Selye’s procedures using monkeys and showed that stressors vary in the amount of stress hormones (adrenaline and cortisol) that they produce, depending on the amount of anger/fear created.
Specific stressors can produce specific patterns of responses (e.g. extreme cold increased cortisol levels, extreme heat reduced them and excessive exercise produced no changes).
There are also gender differences in stress responses (e.g. tend/ befriend in females), therefore it is unlikely stress responses are non-specific.
