Stress - Physiology of Stress & Role in Illness Flashcards
What is stress?
‘Stress’ can have a number of different meanings, one of which is the body’s response in stressful situations. Other meanings can include things that trigger this response (often referred to as stressors), and the perception of a lack of ability to cope with the demands of life.
What is general adaptation syndrome?
This was proposed by Selye (1936), who saw the body’s response as a way of adapting to stressful situations. Over a short term (acute stress) this is helpful, but it can be damaging if the response continues for a long time (chronic stress).
Outline the stages the body goes through in general adaptation syndrome.
Alarm reaction: a stressor is perceived and the body’s response prepared
Resistance: the body attempts to adapt to the stressful situation by releasing stress hormones (epinephrine & cortisol) , which helps to cope with the situation but requires a large investment of resources. If a stressor becomes chronic, the parasympathetic nervous system is activated to conserve energy
Exhaustion: the resources needed to respond to chronic stress become depleted, and the symptoms seen when the stressor first emerged appear again, for example, raised blood pressure and heart rate, sweating, and so on. The immune system becomes compromised and stress-related illness is more likely to occur e.g. hypertension
Evaluate general adaptation syndrome - rats
There is evidence from animal studies supporting the 3 stages of stress responses.
Through exposing rats to various stressors (e.g. forced extreme levels of exercise), Seyle (1936) found
that all rats responded in the same way to both an initial stressor (through
the alarm reaction) and to a prolonged, chronic stressor (through resistance and exhaustion).
Although there are physiological differences between rats and humans in terms of the
complexity of nervous systems and the concentration of (cortisol) hormones released, this nonetheless provides significant evidence for the stages of stress.
Evaluate general adaptation syndrome - monkeys
Mason (1971) found that in monkeys, differing stress responses were shown. For instance, cortisol levels increased in response to excessive cold, decreased in in response to extreme heat, and did not change in response to excessive exercise. This weakens the suggestion that the stress response is the same in all situations.
Outline the acute physiological response to stress
The SAM pathway deals with acute stress by activating the fight-or-flight response.
- A stressor is perceived
- The hypothalamus activates the sympathetic branch of the autonomic nervous system (ANS).
- Messages are sent to the adrenal medulla (the central part of the adrenal glands, situated above the kidneys).
- Stimulates the release of the hormones adrenaline and noradrenaline. The effects of these include raised heart rate, dilation of pupils, tension of muscles, and the conversion of glycogen to glucose, to provide energy.
- Once the stressor passes, the parasympathetic branch of the ANS is activated.
This reverses the effects of the sympathetic branch, returning the person to a state of calmness.
Outline the chronic physiological response to stress
The HPA system deals with chronic stress. This takes longer to activate than the SAM system, but the effects last for longer.
- A stressor is perceived
- The hypothalamus releases corticotropin releasing factor (CRF).
- This sends a message to the pituitary gland in the brain, causing the release of adrenocorticotropic hormone (ACTH) into the bloodstream.
- This travels to the adrenal cortex (the outer part of the adrenal gland), stimulating the release of the hormone cortisol. The effects of cortisol include providing long-term energy supplies to deal with a stressor. It can also have a negative effect on the immune system.
Evaluate the physiological response to stress - beta bias
The fight or flight response may be less applicable to females. This is because preparing to run away from danger would be helpful to survival for males, but less so for females (as their offspring may be abandoned). It has been argued that females respond with a ‘tend and befriend’ characteristic, in order to protect offspring in times of stress.
This means the fight or flight response could be an example of a male-centric viewpoint in psychology.
Evaluate the physiological response to stress - humans and animals differ
Physiological explanations are often researched using animals, and therefore the cognitive aspect of stress is not considered.
It is argued that humans cognitively ‘work out’ whether a situation poses a threat/is stressful, therefore there is more to the stress response than the simple perception of threat by the hypothalamus.
Outline research into immunosuppression (reduced immune system) in stress
There is research to suggest that the stress response prevents the immune system functioning properly, leading to an increased likelihood of illness. The effect of chronic stress was investigated by Kiecolt-Glaser et al (1984):
Aim: To investigate the effect of chronic stress on the immune system.
Procedure: 75 medical students gave a blood sample one month before an exam period (low-stress), and another on the day of their first exam (high-stress).
Findings: The activity of Natural Killer (NK) and killer T cells, which help fight infection by identifying and destroying antigens (foreign bodies such as a virus), was lowered between the first and second blood samples. This was most evident in students who reported more sources of stress, such as a negative life event.
Conclusion: Stress has a negative effect on the working of the immune system, making illness more likely.
Outline Kiecolt-Glaser’s alzhiemer carer study
Kiecolt-Glaser carried out a longitudinal study in 1991, finding that participants who experienced long-term stress (they were caring for a relative with Alzheimer’s) showed decreased immune system functioning and more instances of illness, including depression, than a control group.
What are cardiovascular disorders?
CVDs include any disorder of the heart or blood vessels, which includes strokes.
Outline a study into the impact of short-term stress on cardiovascular disorders
Aim - Wilbert-Lampen et al (2008): To investigate the effects of short-term stress on CVDs.
Procedure: Researchers looked at instances of heart attacks in Germany during football matches played in the 1996 World Cup.
Findings: When Germany played, there were 2.66 times the number of cardiac emergencies on that day, compared with days when Germany were not playing.
Conclusion: Acute stress, such as watching your team play an important football match, doubles the risk of a cardiovascular event.
Outline a study into the effect of long-term stress on cardiovascular disorders
Aim - Yusuf et al: To investigate the effects of long-term stress on CVDs.
Procedure: Participants from 52 countries of differing cultures were included. 15000 people who had had a heart attack (‘MI’) were compared with a similar number who had not.
Findings: Several chronic stressors were linked with MIs, for example workplace stressors and stressful life events. Stress not only caused the CVDs in the first place, but made existing conditions worse.
Conclusion: Chronic stress contributes to the onset of, and severity of, CVDs.
Evaluate the link between stress and illness - HIV
A study found that women who were HIV-positive were more likely to develop pre-cancerous lesions in the cervix if they experienced several stressful life events, compared to those with fewer stressful life events. This supports the link between stress and weakened immune system functioning.
