The GAS model consists of these 3 stages; Alarm – when our HEAP and SAM pathways are activated, causing stress related hormones like adrenaline and cortical to be releases into blood, which in turn, converts to glucose, giving the body a sudden surge of energy, allowing ‘fight or flight’ like behaviors, until the stresses is gone and the parasympathetic nervous pathway activates, allowing us to calm down. Resistance – When the stresses remains however the person appears unaffected on the outside, but Internally the stress related effects are occurring, e. . Stress hormones still being released and a continued elevation in heart rate. The resistance stage can harm health, as the immune system is not as effective. However the body attempts to resist disease. Further stresses make this much harder. Exhaustion – stresses still persists (and would now be referred to as Chronic stress) and Sells claimed that the body’s defenses can no longer cope with the demands that are made, resources are drained, causing a drastic fall In blood sugar levels, and our adrenal glands no longer function properly.

However this Is Inaccurate, which Is a correctly of the GAS model, as while the body is ‘exhausted’ in terms of full ability, it could still perform if immediate action and release of energy was needed. It is also believed that many of the long lasting effects of raised stress hormones is what causes stress related illnesses, rather than the body’s sources being depleted. The study lacks ecological validity with regards to how Sells did much of his testing on rats, using stresses which do not apply to humans.

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Rats are not humans, and are not representative of us in anyway, the studies are not fully applicable to us. Sells also didn’t take into account individual differences, as he disregarded how certain stresses may effect one person drastically, but another, in no/little way at all. However the GAS model was very influential, and was a basis for many others to work from and use for a research guideline, as Sells identified some very important things, such as the fact that the continuing levels of stress hormones affect our body and Immune system.

So other psychologists went on to Investigate these effects. Stones alma was to see the effect of stress on the amount of triglycerides in the blood, and how effective we are at removing them when stressed. He had 70 participants (quite small sample size), 35 male and female who were all aged 40-61 , and were non-smokers, so immediately the exults can be said to be not representative of the whole population, but only a certain sector within those limits. He used repeated measures, which for this Is Ideal as otherwise Individual differences within participants would confound results.

HIS procedure consisted AT lengthen ten people Walt triglycerides, teen leaving teen to rest, then measuring their levels twice a day. And then in his second test, participants were injected with triglycerides, and then informed they had to prepare and perform speech (a fairly stressful task, however one which may have been much less so for a errors who was more self-assured or used to giving speeches due to the nature of their work, unlike a person who is very shy and has no/little experience with such, therefore the actual level of stress will have differed from person to person, which means individual differences will effect results).

However he still found a significant difference between the two different variable conditions, and he concluded that because fats stay in the blood for longer when stressed, they’re more likely to be deposited in veins and arteries, leading to hypertension + CHAD, resulting in death. Combined with the other effects of stress on the body, such as adrenaline increasing heart rate and blood pressure, the chances of health complications arising are massive, as the strain made on veins and arteries could lead to anything from myocardial infarction’s, aneurysms, or thrombosis.

It was noticed that stress directly affects the immune system, inhibiting it, and is known as ‘mispronunciation’. This is because high levels of corticosteroids shrink the thymus gland, which is the place T-cell lymphocytes mature, which are involved in cell-based immunity, and in activating other cells to produce memory cells, required for fighting pathogens in future attacks. Kilovolt-Glasses researched into T-cell activity and the effect stress had on it. She conducted a natural experiment (therefore very high in ecological validity) using 75 med students (small population size, not representative of population).

She took blood samples from each person to measure current lymphocyte activity twice, the first time a month before they each did their final exam (less stress), and the second time during their final exams (high stress). She also gave them questionnaires which meant in-depth qualitative data could be obtained) allowing insight into how each pupil can cope with stress depending on previous psychological stresses and variables, egg life events, or loneliness, anxiety, etc.

Her results showed a significant decrease in lymphocyte activity in the blood samples taken during high stress. However you cannot claim cause and effect, as the results are only correlation. As this experiment is a natural experiment, there is a massive lack in control of extraneous variables, e. G lack of sleep, unmentioned issues, or maybe if they’re genetically inclined to badly react to stress.