- Created by: Jenna k
- Created on: 31-03-14 15:34
The science'y stuff
You will need a back ground knowledge on how a nuron works, how a synaps works and the orientation of the nervous system.
How a nuron works - nurons are specialised units that transport electric impules around the body. Its structur is much like a web with one of it tendrels extendedn. You should know about the cell body which is where the nucleus is held, the dendriets which are the recives for incoming impulses, the axon, axon branches and axon terminal where the electric impulse is passed on from.
On the end of the dendrites and axon terminals there are compents that make up a synaps. When the elcetric impulse travels through the nuron it reaches the axon terminas which has a pre-synaptic terminal where the nurotransmitters are released over the synaptic gap. They are recieved by the post-synpatic terminal that has receptros lining its post-synaptic membrane.
Nurons and synapses have an all or nothing prinicple where is there is not enough energy to move the nurotransitters then it wont move.
How does the body respond to stress?
There are two pathways the autonomic nervous system (ANS) and the pituitary-adrenal system (HPA axis)
ANS > The Hypothalumus stimulates the Sympathomedullary pathway (SAM) to send an impulse from the brain steam down the spinal cord to the adreamal medulla which produces adrenaline and noradrenaline, which increases heart rate and change body tempriture. This is the Sympathetic branch. The parasympathetic branch reduces body tempriture and heart rate to find homeostasis.
The HPA axis starts with the hypothalumous stimulation the pituritory gland to produce a hormone called ACTH. This stimulates the Adrenal cortex to produce coritosteriods which results in a release of gluccorticoides. This means that glucose is released from it stores sorces of glycogen in the liver.
Selye's general addaption syndorme
Selye conducted a study on mice in the 1930's, which consisted of him giving mice daily injections. He noticed that they were deveopling stomach ulsers. However he was not sure whether this was a result of the solution in the injection or the stress of the injection. From this he developed a thee stage model for how our bodies cope with stress.
Stage 1: Alarm The stressor is located and the pituitary-adrenal cortex an sympathomedullary pathways are activated, thus increaing heart rate and tempriture etc.
Stage 2 : Resistance The bodies arousal and hormone level are maintained at a high level.
Stage 3: Exhustion The body reaches a point where the stress becomes chronic and the continuouse high levels of hormones lead to stress related illnesses.
Evaluation - Selyes work has been very infuential in stress research but he did not take into account induvidual differances and cognitive elerments of stress. This has lead to the change in thoughts about the casue of stress related illnesses. It was suggested to be due to exhustions but now they think it is due to the chronic stress and the maintained high levels of stess hormones.
The immune system.
Types of stress > Acute time limited (a unplanned stress lasting for minutes), Brief naturallistic (Everyday stessors that may last months or years) and chronic stressors (Long term stress that doe not go away like exams do).
Natural immunity consists of leukocytes (phogocytes and macraphages and natural killer cells.) These cell engulf the pathogens and disolve them using lysosoms.
Specific immunity consists of Cellular and Humeral immunity. Cellular immunity consists of T cells being produced form the thymus gland. These T cells inculde T killer cells, T memory cells snd T helper cells. They attack and destroy intracellular pathogens. Humeral immunity consists of B cells produced in the bone marrow. This involves the secretion of antibodies and memory B cells that destroy extacellular pathogens. The memory cells in both types of immunity keep some of the atibodies so if the pathogen returns then the body has a better chance of betting it quicker.
Cohen et al 1991
Cohen developed a Stress index score.
Aim: He wanted to investigate the effects of stress on our suseptablelity to a common cold.
Method: He Used 394 participants, who completed the stress index and were awarded a score. They then were given a gold virus in the form of nose drops.
Findings: People with a higher stress index score were more suseptabe to the cold. Half of the participants with a stress index of 11 or 12 caught the cold. Over all 82% of the participants caught the cold.
Conduction: He conculded that the higher your stress index then the less active and effect your immune response are.
It's not ethical to give a healthy person a cold. It showed a realtionship and a correlation but it did not show a cause and effect and therefore cant be regarded as hard proof. This is furthered as there was no manipulation of the independant vairble.
Keicolt-Glaser et al 1984
Aim: They wanted to prove that stress has a physiological effect on our immune system.
Method: They took blood sample of 75 medical students before and during their exam period. They were looking for the amount of natural killer cells. The students also completed questionnaire based on their negitive life events and social isolation.
Findings: They found that in the exam period there was a lack of netural killer cells compared to before the exam period. This was alos raised for those that felt more socially isolated.
Conclution: They Concluded that Stress directly influances the productivity of the immune system making people more valnerable to illness.
It was a natural study and no harm was caused to the participants. Thus it has a high ecological validity and relivance to the target population. However there may have been some Acute-time limmited stress caused by the blood sample, but this would not have casue much change in the results. Compared to Cohen this sttudy is very ethical.
Aim: He wanted to investigate the immunosupression of stress.
Method: To do this he meaured lymphocytes in blood and placed them in a centralfugue for 1 hour. He repeted this for 5 hours. He did this wthl mice too. He injected a mouse with cancer and left in in a calm environment. He them injected another with cancer and spun them for 5 hours.
Findings: Hs finding showed that the cancer in the mice that were spun had spread rapidly where as the mice in the calm enviroment had stayed the same size.
He conculded that when understress the immune system became supressed, thus making the cancer grow.
This has now lead to the change in hospitals and the creation of Hospises.
Daily hassels: Holems and Rahe life changing event
Rahe and Holmes were both medical doctors who saw a correlation in the amount of their patients that had stressful lives. They divised a Stress index by asking 392 of their patients to order a number of events that were most stressful in their lives. They added these up and called them life changing units. They then asked the patients to tell them what had happend to them over the last 12 months, interms of the list devised. They found that if the patients had life changing units over 300 them they were at risk of anxiety and heart attacks.
They conculded that it was infact the life changin events that cause the most stress that made them sick and not just stress in general.
Rahe et al 1970
In 1970 Rahe put his theory to the test in the field.
Method: He studies a crew of 2500 American navy personal for 6 months on board the SRRS. Before they boarded they completed the Life change events questionnair and it gave them life change units. While they were an the ship there were regular medical checks and every illness was recorded. At the end of the 6 months the doctor gave them a health score. This was paried with the LCU's.
Findings: There was a positive correltaion of 0.118 between LCU's and the health score.
Concultion: He conculded that there was a correlation between life change events and the development of stress realted illness.
Evaluation: There was a large contained sample that was easily controlled and manipulated. This gave way to it being a naturalistic study which is highly ecologically valid in the civil servant population. However it is not generalisable to civilians.
The study was gender and culture bias and the tour would have been a stressful situation so it is not possible to draw a cause and effect form the results and generalised them the the population.
Anita DeLongis et al 1982
DeLongis conducted a longitudinal study over 9 years with the aim to prove that stress related illness are not just due to life chaning events but the daily hassels of our lives too.
Method: She did this by asking 100 male participants aged 45- 64 form Sarfancisco to look back over the last 2 and a half years and record any major life changing events. She then asked them to fill out 4 questionnairs every month for a year. They recorded health status, Life events, Hassels and uplift scales.
Findings: She found that daily hassels decrease our heath while uplifts increased our health. She also found that there was a strong correlation with the amount of daily hassels and our health.
Concultion: Thus she conculded that it was the smaller stressors that affected our health more that the life changing events.
The study would have become a daily hassle and would have become boaring for the participants taking part in the study. Thus making the results unreliable as the participants may have given up putting all their effort into them.
Work place stressors.
Home work interface > A source of stress in the workplace, in which emplyees try to balance the demands of work and home resonsibilities. (work load)
Decision latitude > The sense of control and induvidual has over their worjload and how it is organised. High dicision latitude is linked to lower vulnerability to stress related illness. (Control)
Work place stressor > aspects of the work place environmet that causes a stress response in our bodies.
Marmot et al 1997
Aim: He wanted to investigate the relationship between control in the work place and incedants of coronary heart disease.
Method: He studies 7372 civil servants aged betwenn 35-55. He asked them to be screaned for CHD and to complete a questionnaire designed to test job control. The results were organised into 3 groups. The Administrator, executive and support staff. This was known as white hall 1. White hall 2 consited off moitering the groups over a period of 5-7 years.
Findings: He found that the lower payed jobs had lower control, which increased the rick of CHD.
Concultion: He concluded that there is a relationship between work control and incedants of CHD.
They used a self report method which could have lead to Social desirabilityes. Also there is a correlation but not a cuase and effect. There is cultural bias as they were all english participants and there were induvidual differances. Which we will explore later in this book.
Johansson conducted a study in a Swedish saw mill.
Aim: He aimed to invesigate whether the workers stressors, such as control and work load, increased levels of stress related psychological arrousal.
Method: He studies cleaners and Finishers in this saw mill. The finishers had to finish the wood so it could be sold at the end of the day.They had a high work load and high pay to go with it. They also solidified the other emplyees wadges as they made the woof saleable. The cleaners came in at night and cleaned the set premisses. The cleaners had all night and a team that they could coordiate in any way they wanted, as long as it was all clean by the morning. They have low work load but high job control.
Anyway they each had to do urin samples when they were at work and at home. They also kept a record of who had days off due to illness. The urin sample measured the levels of adrenaline and noradrenaline.
Findings: He found that the Finishers had more days off sick. But both the cleaners and the finishers had higher adrenaline level at work then they did at home. However over all finishers had the higher level of adrenaline in their system.
Concultion: A combination a of stressors which lead to coronical phyciological arrousal. which causes Stress related illnesses. eg. Lack if control, machine passed work, high work loads ect.
How has research into stress in the work place lea
As a result of Marmot and Johanssons research there is now:
- more brakes if working with machines.
- Making sure that there is social interaction (Johansson's saw mill every cleaner could interact while the finishers were working under loud noise so couldnt hear each other, thus increaseing adrenaline levels.)
- We can set our own deadlines.
- Increased ablilty for emplees to control what they are doing.
- Make sure the environmental factors are suitable. (tempriture, ventilation etc)
- Intoduce flexi-time so there is more control.
- Share responisbilities between a team.
There are two differant personalities Type A and Type B. Type A is competitive, Hosile, Agressive and restless. While Type B are calm, easy going, relaxed and in no way conpetitive.
Friedman and Rosenman 1974
Aim: To research the link between personality type and the risk of CHD.
Method: They studied 3000 healthy american men aged between 39-59 for 9 years. They were first assesed on their personality type and then monitered over the next few years. The participants personality was determined through an interveiw, they were asked about their eating habbits and how they responed to stressful situations. Their behaviour during the interview was also asseced. They were spilt roughly into two groups Personality type A and not type A.
Findings: Over the course of 9 years 257 men died. Over 70% were type A personalities.
He conculded that people who are type A personalities are mor susceptible to stress beacsue of their behaviour traits. And therefore they are more likely to suffer form stress realted illness' and CHD.
The sample was large however it was culture and gender biased. They conducted an interview which is a reliable method although there is still some doubt about social desirabilities. It was a natural experiment and therefore had a lot of ecological vailidy.
Kobasa's Hardy personality
Kobasa thought that there maight b a personality thay would be resistant to stress. They would be commited (invovled in what they do), challenged (see stressful situations as a challenge) and controled (Stong sense of personal control).
Aim: to porve that there is a hardy personality.
Method: She studies 600 American men, whom were all buisness managers form a vary large compagny. They completed personality questionnaires and reported on illness in the last 3 years as well as the amount of stressful incedents in their lives. All the men scored highly on the stressful life events.
Findings: Although all of them had high stress there was a proportion of them that did not become ill becasue of it. These people are the hardy personalities.
Conclution: That the hardy personaliy does exist and they are more resistant to stress that most of us.
Evalutaion: The sample was a good size but there was bias. There is only a correlation and not a cause and effect. These people may just be pesimestic or anomilies and they are diffucult to access.