This is the acute (immediate) response to stress (it uses electrical signals). Higher brain areas (Cortex) detect and perceive something as a stressor, triggering the Hypothalamus, which in turn activates the Sympathetic branch of the Autonomic nervous system, stimulating the Adrenal Medulla, producing two hormones, Adrenaline and Noradrenaline, which cause the Fight or Flight response, which causes bodily changes and has evolved for survival.
Bodily changes may include: an increase in heart rate (to carry around oxygen around the body quicker); an increase in blood pressure (veins and arteries narrow so blood pumps faster); an increase in muscle tension (which increases reaction time) and the dilation of pupils (helps one to be more aware of one’s surroundings).
· H. P. A (Hypothalamic Pituitary Adrenal Axis) This is the chronic (slow, long-term) response to stress. Higher brain areas (Cortex) detect and perceive something as a stressor, triggering the Hypothalamus, which in turn release the hormone CRF, which activates the Pituitary gland in the brain, releasing the hormone A.C. T. H, which activates in the Adrenal Cortex – this releases corticosteroids (e. g. cortisol) that cause the liver to release glucogen (fats and sugar), which provide continued energy for the Fight or Flight response. In the long term, corticosteroids can suppress the immune system. How stress can affect illness:
· Direct Effect This is where stress directly causes an illness of the malfunction of the immune system. For example, coronary heart disease has been shown to the have a link with the S. A. M response.
It is caused by increased heart rate and narrowed arteries (which are results of the Fight or Flight response, brought about by the S. AM response) which cause increased fats and sugars blocking arteries, as well as putting more pressure on the heart. High blood pressure and strokes are also linked to stress. · Indirect Effect This is where stress may make people more vulnerable to illness, as it may weaken the immune system. Some people inherit a weak immune system and stress may make them even worse. Lifestyle also affects the immune system and stress may cause such behaviours to increase.
For example, when one is stressed they may turn to drinking, drug and tobacco use, etc or change their sleeping and eating habits – or even going out all night partying. All these things can suppress the immune system if done frequently. The relationship between stress and illness may be seen as very complex. Research into stress and illness · Keicolt-Glaser et al (medical student study) The aim of this study was to see if exam stress may affect the functioning of the immune system; it was therefore a natural experiment, using a volunteer sample (which consisted of 75 first-year medical students) and repeated measures.
The procedure was as follows: blood samples were taken of all the students one month before their exams (this was defined as a low stress period) and again on the first day of their exams (this was defined as a high stress period). These blood samples measured the participants’ immune functioning by counting the number of leucocytes (natural killer cells & T cells) – if there was a high number, this meant a strong immune system. If they were low, it meant the opposite. It was found that in the high stress period, the number of killer cells and T cells were low, whilst in the low stress period, the number was high.
There was, therefore, a negative correlation between exam stress and immune functioning. It was concluded that there was indeed a link between the two – exam stress is associated with immunosuppression. However, stress is only one factor that may affect the immune system. A weakness of this study is the sample – they were all first year medical students – this is not representative as the group cannot be generalised to other students, ages or groups. Also, they are volunteers – the sample is therefore biased as volunteers are ‘unusual’ or ‘extra-motivated’ – it lacks population validity, which in turn leads to an inability to generalise.
However, Keicolt-Glaser has carried out research using Alzheimer’s carers and married couples and found similar results – this makes the findings of this study more reliable and is in fact can be generalised to slightly more groups. L It is also a natural experiment; therefore the study has high ecological validity and mundane realism as the situation was real and was not manipulated by the experimenter. As it is such a natural situation, there is also a significantly smaller chance of participants responding to demand characteristics; it is unlikely that they were able to consciously affect their blood test.
J However, this type of experiment essentially means that no extraneous variables that could potentially affect the results were controlled – therefore, we cannot be sure that the level of stress is what affected immune functioning alone. There are many other factors, including lifestyle and genetics, which were not considered – this questions the validity of the results. LIt is also impossible to replicate the experiment and therefore we cannot see if the results found in this study are reliable.
L The findings of this experiment were merely a correlation, therefore it only proves that there may be a relationship between the two co-variables – this is positive in the sense that it avoids ethical issues as no variables are being manipulated, merely measured – the “participants were protected from harm” as no stress was deliberately caused.
J However, correlations mean that it can never be proved that the exam stress caused the change in immune functioning due to the other (confounding) variables that have not been controlled or taken into account such as medical conditions and lifestyle (such as sleep problems and eating habits etc.).
L The method used to measure immune functioning has been deemed as inadequate – the immune system is complex – T-cells and natural killer cells are only one aspect – it is therefore too simplistic and difficult to know whether the immune system is weak from this alone – different parts may be stronger to compensate for it, such as fast wound healing. L · Keicolt-Glaser (Alzheimer’s carers and married couples) She tested the impact that conflict between spouses could have on the length of time wounds took to heal.
It was found that blister wounds on the arms of husbands and wives healed more slowly after a conflicting discussion or argument – this was seen more in women than in men. She also found that carers of Alzheimer’s disease sufferers took significantly longer to heal minor arm wounds. Looking after the relative or the patient (a major stressor) may have suppressed the immune system which can be dangerous. However, these studies use a very small and unrepresentative sample, therefore they lack population validity and they cannot be generalised.
LThey were also natural experiments, and therefore we cannot prove cause and effect, nor see if the results are reliable as we cannot replicate them – there may be other factors – genetics, the type of stress, personality, culture etc. that may cause the findings. L · Cohen et al (Common cold study) This was a lab experiment and 394 volunteers were exposed to the cold virus. Their level of stress was then assessed via a questionnaire. It was found that there was a positive correlation between stress level and the likelihood of developing a cold.
However, questionnaires were used – these may be unreliable as participants are liable to giving socially desirable answers which therefore questions the validity of the results generated by the questionnaire. LAlso, the findings were only a correlation, so it cannot be proved that stress caused the cold as there are other variables that were not controlled. LVolunteers were also used, so the study is lacking in population validity and is not representative. L · Marucha et al (dental students and biopsy study) The effect that stress had on healing was tested on 11 dental student volunteers.
They underwent a small biopsy on the roof of their mouth at two occurrences; the first being at the beginning of their summer holidays (defined as low stress) and the second six weeks before exams (defined as high stress). The healing of the wound was monitored and recorded, using videos of the mouth. The rate of reduction in wound size was measured at the two levels of stress. It was found that students were 40% slower to recover in the “high stress” period. This suggests that stress can affect how long it takes a wound to heal as the immune system is suppressed.