Body's Response to Stress &
Stress and the Immune System
SAM pathway (fast acting, acute stress)
hypothalamus activates sympathetic branch of the ANS, stimulating adrenal medulla
This leads to the release of adrenaline & noradrenaline (fight or flight
response e.g. increased heart rate, raised blood pressure, sweating)
Parasympathetic branch works afterwards to calm these processes e.g. increased heart rate, building up energy for future use
PAS pathway
hypothalamus stimulates the pituitary gland to produce hormone ACTH
ACTH stimulates the adrenal
cortex, producing cortisol
If stress is acute, effects on immune system small, even could have upregulation effect
Chronic stress, however, causes down regulation in immune function because
of increase cortisol levels, which cause a shrinkage of the thymus gland
shrinkage of thymus glands means less white blood cells,
leaving the body vulnerable to infections e.g. viruses
Kiecolt-Glaser et al
Blood samples taken from medical students,
before final exams (low stress) and during
exam period (high stress). Ps also carried out
questionnaires to assess social isolation &
negative life events.
White blood cells significantly reduced in high stress condition
concluded that examination stress reduces immune function
Evaluation
- natural experiment, so IV not controlled, cannot infer causal link
+ exam stress is a natural form of stress
- sample is medical students, unrepresentative
+ natural study, fewer ethical implications
Cohen et al
exposed Ps to cold virus, and after 7 days,
measured whether they had caught a cold
and measured stress via 'stress index score'
Evaluation
- research is correlational, cannot infer the causal link,
other factor could play a part such as smoking and drinking
correlation found between stress index score and developing a cold
Evaluation of research into stress and the immune system
+ Useful applications
- Reductionist, ignores other factors such as depression & anxiety that are difficult to control
- Ignores individual differences such as genetics, age and personality factors
+ Good experimental support
Stress and cardiovascular disorder - increase in heart rate may wear away lining of blood vessels, causing increased risk of atheroma. Person who experiences more chronic stress, more at risk of CHD