Stress as a bodily response
Stress as a bodily response...
TWO main ways our body responds to stress and both involve adrenal gland (2 sections of the gland - Adrenal cortex and adrenal medulla)
THE SYMPATHOMEDULLARY PATHWAY (short term)
the autonomic nervous system (ANS) role is to maintain the normal functioning of bodily systems in response to demands.
- sympathetic subdivision - when activated... heart rate and blood pressure increase, fats and carbs are mobilized, activity in digestive tract slows down = sympathetic arousal
- parasympathetic subdivision - when activated... heart rate and blood pressure return to normal and digestion speeds up.
The adrenal medulla is controlled by the ANS and activation of the sympathetic branch stimulates it to release the hormones adrenaline and noradrenaline.
TOGETHER the hormones reinforce the pattern of sympathetic activation = heart rate and blood pressure increased.
THE PITUITARY ADRENAL SYSTEM (long term)
- Under the contol of the hypothalamus and pituitary gland.
- Higher brain centres evaluate a situation as stressful, instructs hypothalamus to release CRF (corticotrophin releasing factor) which travels to pituitary gland.
- Pituitary gland releases the hormone ACTH.
- ACTH travels to adrenal cortex and stimulates the release of the hormones corticosteriods into the blood stream.
Activating the body's stress response
Activating the body's stress response...
The two systems, when aroused, prepare the body for energy expenditure. Corticosteriods, adrenaline and noradrenaline mobilize energy reserves and sustain blood flow and heart rate to get oxygen to the muscles.
The General Adaption Syndrome (GAS)
- Alarm - stress reponse = systems activated
could be a threat, injury, illness affecting body
- Resistance - body copes with stress
coping with the stressor, so from the outside it seems under control
- Exhaustion - stress-related illness may develop
if the stressor is long lasting/chronic then damaging effects of stress can occur.
'Fight or flight' or 'tend and befriend' - gender differences in the stress response:
In 2005, of the 33,000 people in the UK who died of coronary heart diseasse before the age of 75, 70% men, 30% women - can be the way our ancestors dealt with stress which now determines the way we react now.
Stress-related illness and the immune system
Stress-related illness and the immune system:
IMMUNE SYSTEM = main defence against infection by foreig agents. Any agent that stimulates an immune response is called an Antigen, such as bacteria, viruses and fungi (moulds/yeasts.
WHITE BLOOD CELLS = key player in our immune system are the white blood cells, which are manufactured int he bone marrow and circulate in the bloodstream..
2 types of white blood cell are lymphocytes and phagocytes which provide 3 different mechanisms of immunity:
- non-specific immunity - phagocytes are cells that surround and ingest foreign particles wherever they encounter them. E.g. macrophage, which also activate helper T cells.
- cell-based immunity - Lymphocytes called T cells seek out and destroy any cells recognized as foreign and cells infected with antigens. Helper T cells activate cytotoxic T cells which destory infected body cells and activate another class of lymphocyte - the B cell.
- antibody-based immunity - B cells destory invading agents while they are still in the bloodstream and before they enter the body's tissues - form plasma cells which produceantibodies. Attach themselves to the virus/bacteria.
HIGH LEVELS OF CORTICOSTERIODS CAN SHRINK THE THYMUS GLAND, which prevents the growth of T cells. Even short-lasting life events, such as marital strife, can cause immunosuppression, while chronic (long term) life stress causes parallel long-term reductions in immune function. Can be improved by exercise, diet and social support!
some effects of stress on the immune system:
- infection and diseases - stress causes physiological changes that tend to weaken our immune system... illness occurs more frequently and recovery takes longer.
- indirect effects - anti-inflammatory hormones released which inhibit immune cell functioning.
- psoriasis and eczema - systems of inflammatory skin disorders worsen with stress as stress interferes with the immune system's ability to deal with the inflammation.
The effects of stress on the immune system - KIECOLT-GLASSER (1984) a study of the effects of important exams on the functioning of the immune system.
AIM: to investigate whether the stress of important examinations has an effect on the functioning of the immune system
PROCEDURE: natural experiment, 75 medical students. Blood samples taken 1 month before exams and during exams. Immune function assessed by measuring T cell lymphocyte activity in the blood samples. Students given questionnaires to asses psychological variables (life events etc)
FINDINGS: T cell activity significantly reduced in the second blood sample taken during exams compared with first sample. T cell activity was most reduced in ppts who reported high levels of life events and loneliness.
CONCLUSION: exam stress reduces immune function, potentially leaving individual vulnerable to illness/infection. Immune function is also affected by psychological variables such as stress of life events.