Stress REVISION Autonomic Nervous System controls involuntary body
Stress REVISION
Autonomic Nervous System (controls involuntary body functions e. g. heart, breathing, digestions etc. ) SNS: Highly responsive to stimuli Prepares body for intense physical activity PNS: Maintains equilibrium by calming the body and inhibiting high energy functions
Sympathomedullary System Key Areas
SAM
Hypothalamic Pituitary Adrenal System Key Areas
HPA
Immune System • IMMUNE SYSTEM: billions of cells travelling through blood stream Ø WHITE BLOOD CELLS: (major cell in immune system) protect body from antigens Ø ANTIBODIES: produced by white blood cells to destroy antigens • ANTIGENS: foreign bodies e. g. bacteria, viruses, cancerous cells • IMMUNOSUPPRESSION: HPA stress pathway temporarily supresses immune system • Occasional cortisol production helps protect against viruses and heals injured tissues • Continuous cortisol production (i. e. chronic stress) can interfere with white blood cell activity and production of antibodies.
Research into Stress & Immune System Describe Studies (AO 1) COHEN ET AL, 1993 KIECOLT-GLASER ET AL, 1995 • Aim: investigate effects of stress on resistance to disease • Aim: investigate whether stress has an effect on the functioning of the immune system • Procedure: (Lab Experiment) • Procedure: (Natural Experiment) Ø 394 Healthy ppts Ø 75 volunteer university students ØStress levels assessed using questionnaire Ø Blood samples taken: One month before final exams (low stress); during the exams (high stress) ØTest Condition: nasal drip of common cold ØControl Condition: nasal drip of saline solution ØPpts quarantined – illness assessed Ø Immune functioning assessed by measuring T-Cell activity in blood Ø Additional test: Stress levels assessed using questionnaires (life events & loneliness) • Results: 82% caught cold virus; + Correlation between development of infection and stress levels Ø Findings: T-cell activity reduced in high stress sample. Most reduced in students who reported high levels of life events & loneliness • Conclusion: Stress depresses efficiency of immune system Ø Conclusion: Stress reduced the effectiveness of the immune system.
Research into Stress & Immune System Evaluate Studies (AO 2) COHEN ET AL, 1993 KIECOLT-GLASER ET AL, 1995 Sample: Large (good generalisability) Natural Experiment: High Ecological Validity Self-report technique = demand characteristics (poor internal validity) Sampling bias: All students; exam related stress (poor generalisability) Correlational Study: can’t show causality; makes true interpretation of results difficult Poor control over extraneous variables: Cannot say with certainty that exam stress caused weaker immune system / Ethical considerations: protection from harm – but scientific findings outweigh this Poor measure of illness: Cell activity reduced, but illness not documented - changes may be too small to be seen as ‘illness’. Correlational Findings: can’t show causality; makes true interpretation of results difficult
Research into Stress & Immune System General Evaluation (AO 2) Historical Importance: Results provide support for idea that having high levels of general stress reduces the ability of the immune system to fight off viral infection Practical Implications: Health practitioners can use findings to anticipate problems occurring due to stressful incidents and use appropriate therapies. Causality: can’t be sure that stress has direct effect on problems with immune system. Other factor such as poor diet or lack of sleep may also contribute Acute/ Chronic Stress: difference in effects of acute and chronic stress. Acute stress is short-term and can even result in improved immune system functioning. Lack of longitudinal evidence: Effects of stress on immune system are likely to take some time to occur. Longitudinal studies could offer more accurate findings.
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