On top of each kidney we have the adrenal cortex and adrenal medulla, together called the adrenal gland, in the brain we have a vital area known as the hypothalamus, also in the brain and connected to the hypothalamus there is the pituitary gland. The pituitary gland is the main endocrine gland; it controls the release of many hormones. In the brain stem we find the autonomic nervous system, which runs to different organs in the body e.g. heart and lungs.
The ANS has two divisions; the sympathetic (prepares to cope with a dangerous or stressful situation) and the parasympathetic division (calms us down).
During a state of arousal/stress, the sympathetic division of the autonomic nervous system stimulates the adrenal medulla to release the hormones adrenaline and non-adrenaline into the bloodstream. These hormones, in conjunction with corticosteroids, reinforce sympathetic arousal by stimulating heart rate and mobilizing further energy resources in the body. This enables the body to deal with the stressor by activating a ‘flight or fight’ response.
Seyle produced a model known as the General Adaptation Syndrome to explain the short term effects of stress, it also helps us understand the development of stress related illnesses e.g. ulcers. He identified the following three stages of a physiological response to stress:
Stage 1 – Alarm – stress response systems are activated e.g. internal – injury, external – nasty dog;
Stage 2 – Resistance – stress response is fully activated and body is coping;
Stage 3 – Exhaustion – as a result of this chronic long lasting stress, the body’s resources become depleted and exhausted and result in physical illnesses e.g. ulcers and depression.
There is increasing evidence that stress can cause illness by impairing the workings of the immune system. The immune system protects the body from harmful viruses and bacteria cells known as lymphocytes recognise and destroy harmful viruses and bacteria.
When the stress response is activated, the activity of the immune system is slowed/scaled down.
One of the earliest studies into the effects of stress on the immune system was conducted by Riley 1981 using mice. He placed the mice on a rotating turntable thus creating stress. Riley measured the mice’s lymphocyte count over a five-hour period and found a marked decrease, indicating suppression of the immune system. He also looked at the link between stress and tumour growth by implanting cells in mice, one group had ten minutes of rotation per hour for three days – high stress group, another had no stress. Riley found that the mice with no stress developed no tumours whereas the high stress group of mice developed large tumours. This study raised an ethical issue about the use of animals in lab tests/experiments. Also we should be cautious about generalising the findings from animal studies to humans, our pressures (concerned with relationships, money, work etc) cannot be likened to animal studies which induce stress over a short period of time.
Another study was done by Kiecolt-Glaser et al 1995, she looked at humans and compared the wound healing rates in ‘high stress’ women who were caring for relatives with Alzheimer’s and had a ‘stress free’ matched group. The ‘high stress’ group took considerably longer (9 days) to complete healing a wound.
This shows the study between stress and the body’s ability to heal and its response to infectious diseases has important consequences for people undergoing and recovering from major surgery.
This study also showed that under conditions of stress, the levels of adrenaline and non-adrenaline increase these increases can suppress aspects of immune function, including killer T cells. This suppression then raises risk of viral infection.
Cohen et al 1993 wanted to establish whether high levels of stress would cause suppression of the immune system. They chose 154 men and 266 women and measured their stress levels using a life event covering the previous year, how they perceived their stress levels and a negative affect (emotion) scales, anxiety, fear, depression. They exposed the volunteers to nasal drops containing bacteria of colds. The experimenters combined scores on the three scales to produce a psychological stress index for each person.
They found a difference between groups with low scores in the stress index and those with high scores. The highly stressed volunteers developed significantly more clinical colds.
The problem with looking at the effects of stress on the immune system is that it may be affected by a whole range of factors in people’s lives and so there may be an indirect relationship between stress and illness e.g. individuals who are stressed may smoke or drink more this leads to an unhealthy individual. Also the immune system is very complex.
Cardiovascular disorders such as heart disease and circulatory problems are caused partly by stress and partly by other ‘risk factors’ e.g. diet, smoking, alcohol consumption and exercise.
Friedman and Rosenman in the 1950s were interested in examining the role between diet and coronary heart disease (CHD). They found that American men were more susceptible to heart disease than American women, even though their diets were very similar. They thought that job-related stress might be a contributing factor as most men worked, most women didn’t.
In a later study they found that accountants who were approaching a tax return deadline had a dangerously high level of serum cholesterol and a high blood clotting speed, which then returned to normal after the deadline.
Friedman and Rosenman 1974 looked at 3000 men between the ages of 39-59 years. They were dived into two group type A – ambitious, competitive, easily angered and perfectionists. Type B – relaxed, easy-going, not driven to achieve perfection and not easily angered. They found within nine years of commencing the study 70% of the 257 who died were type A individuals (they took smoking and drinking into consideration). Therefore personality type and stress are closely related and together are related to the risk of CHD
There is however, an unclear relationship between CHD and Type A personalities because they are more likely to have other known risk factors.
Stress itself cannot cause CHD or any other illness. It is somehow linked to cardiovascular disorders and appears to play a role in hypertension – when a person experiences several weeks of high blood pressure and it’s a major risk factor of CHD.
