The Body's Response to Stress
The Fight or Flight Response
WALTER CANNON (1914) argues that this was an adaptive evolutionary response in our early ancestors.
During the alarm stage, several changes happen to the body automatically:
- heart beat speeds up
- breathing deepens
- sugar/glucose levels rise
- saliva and mucus dries up
- skin goes pale
- pupils dilate
After the emergency is over our physiological levels of functioning return to normal.
Selye's General Adaptation Syndrome (GAS)
HANS SELYE (1956) - Defined stress as the non-specific response of the body to any demand made upon it.
- The GAS comprises three stages: ALARM reaction, RESISTANCE and EXHAUSTION
- By the last stage resources are becoming depleted and psycho-physiological disorders develop such as high blood pressure, coronary artery disease and coronary heart disease.
- FRIEDMAN & ROSENMAN (1974) found evidence for the role of individual differences in mens ways of dealing with stressful situations. The concluded that men who displayed type A behaviour (TAB) were more likely to develop CHD than other men
In summary, Hans Selye suggested that all stressors produce the same range of physiological responses and persistant stress may produce psychosomatic illnesses such as hypertension, cardiac disease, migrane, gastric ulcers and eczema.
The Pituitary-Adrenal System and Sympathomedullary
Most psychologists regard the hypothalamus as the starting point for the stress response, it initiates a hormonal response known as the hypothalamic-pituitary adrenal axis.
Threatening or worrying events activate the hypothalamus which stimulates the release of a hormone known as corticotrophin-releasing factor (CRF). CRF targets the pituitary gland.
The pituitary gland (sometimes known as the 'master gland') is divided into two parts, the anterior (front) and posterior (back). In response to CRF the anterior pituitary gland begins to release a hormone known as adrenocorticotropic hormone (ACTH) which travels in the blood to the adrenal glands.
Adrenal gland is made up of two parts: the adrenal cortex (outer part) and the adrenal medulla (the centre or inner part). When someone is aroused the sympathetic division of the autonomic nervous system (ANS) speeds up bodily activity. This involves increasing heart rate and stimulating certain glands, including the adrenal medulla to secrete the hormones adrenaline and noradrenaline which further increase arousal.
together this response is described as the fight or flight response, the immediate arousal response to a stressor. This is likely to be an evolutionary response. Een today when humans feel aggressive and fearful there are large increases of adrenaline and noradrenaline in our systems.
Stress-related Illness and the Immune System
The immune system is a collection of cells that travel through the bloodstream defending the body against foreign bodies (antigens) such as bacteria, viruses and cancerous cells. The main types of immune cells are white blood cells (leucocytes). When we're stressed,our immune stystems ability to fight off antigens is reduced, therefore we are more susceptible to infections.
This was demonstrated by Glazers study of medical students facing important examinations, and in Schliefer's study of men whose wives had died from breast cancer. Riley's study of mice stressed out by being placed on rotating turntables also helps to demonstrate that different stressors are all involved in reduced immune function.
- Glazer (1986) assessed 40 medical students 6 weeks before they took important exams.He asked students to complete a questionnaire and took blood samples. He medically assessed the students during the time of the exams by taking more blood samples.
- During exams Glazer noted high levels of adrenaline and noradrenaline, the 'stress hormones', we know there's a direct link between these hormones and the immune system.
- Glazer observed a significant reaction of T cells during the exams. The reduction of T cells is one method used to assess whether the immune system is suedppress.
- A few weeks after the exams, T levels were back to normal. Glazer concluded that the students had been under a lot of stress and that different types of stress are all involved in reduced immune system.
Life Changes and Daily Hassles
Holmes and Rahe (1967) constructed an instrument for measuring stress. They defined stress as the amount of change a person has to deal with during a particular time. Their Social Readjustment Scale (SRRS) comprises 43 life events, each given a life change unit (LCU) score.
- They found that the higher someones overall LCU score, the more likely they were to show symptoms of both physical and psychological illness. They claimed stress actually makes us ill
- The SRRS was the first attempt to measure stress objectively and examine its relationship to illness. It assumes any change is stressful, but the list of life events is largely negative.
- So the SRRS may be confusing 'change' with 'undesirability' and there is no reference to the problems of old age, or natural or man made disasters. Only life events that can be classified as out of a persons control are correlated with later illness, and the life events don't include everyday hassles such as traffic jams etc.
- Retrospective studies like this can sometimes produce unreliable data.