- Created by: Sarah
- Created on: 28-05-11 15:10
Outline the two stress pathways (6 marks)
The acute stress pathway uses electrical impulses to send messages throughout it. It begins at the hypothalamus which activates the sympathetic branch of the autonomic nervous system (ANS) when there is an external threat to the body. This then sends a message to the adrenal medulla, which releases adrenaline and noradrenaline. These have the effect of increasing heart rate and blood pressure, while mobilising fat and body sugars around the body. This helps form the 'fight or flight' response where the body becomes ready to fight or flee.
The chronic stress pathway responds to prolonged stressors. It begins at the hypothalamus, which sends chemical impulses (CRF) to stimulate the pituitary gland to release ACTH. This stimulates the adrenal cortex, which secretes corticosteroids such as cortisol, which has the effect of suppressing the immune system.
Outline and evaluate research into stress and the immune system (12 marks)
There has been lots of research into the effects of stress on the immune system. It all proves a clear link between stress and the immune system but it can always be criticised due to methodology.
Kiecolt-Glaser et al (1984) was a natural experiment done on medical students who had exams at the time of the research. The experiment aimed to measure T cell activity as T cells aid the immune system to fight off disease/illness. Blood samples were taken a month before the exams and during the exam period to measure this; a questionnaire was also given to measure loneliness and life events. Results showed that T cell activity decreased during exams and it was particularly low in those who reported feeling lonely etc.
Marucha et al. (1998) used a punch biopsy to inflict a wound in students' mouths to see how long it took for the wound to heal under the exam period conditions and in the summer holidays. Results showed that the punch biopsy administered 3 days before an exam took up to 40% longer to heal than in the summer holidays.
Evans et al. (1994) looked at measuring the antibody SigA in students who were experiencing acute stress, such as giving a speech, or experiencing chronic stress, like their exams. Results showed that SigA increased when the students experienced acute stress, but decreased when they experienced chronic stress. So essentially this shows that short-term stress can actually be beneficial to our health, but long-term stress has a negative effect on the immune system.
This research has it's positives, such as all of the research shows a clear link between the effects of stress on the immune system, as well as showing the link is not a simple one, e.g. Evans et al. showed that not all stress has a negative effect. The research also used a naturally occurring stressor: exams. This means that they have mundane realism and high ecological validity as the task was not unrealistic and took place in their natural surroundings.
However, they can all be criticised in some way. Kiecolt-Glaser et…