Section 1 Two bodily responses to Stress:
S.A.M (Sympathetic Adreno-medullary Pathway)
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