Stress

• when faces with a stressful situation, an animal responds with fight or flight. 
• called the sympathomedullary pathway (SAM system) 
• S - sympathetic nervous system - a branch of the autonomic NS that is activated when a stressor is seen 
• M - adrenal medulla - a signal is sent to the two endocrine glands (adrenal glands) located above the kidneys. The adrenal medulla is activated (middle part) and releases adrenaline and noradrenaline into the bloodstream 
• A - adrenaline and noradrenaline circlate through the body and affect targer organd such as the heart and muscles, and causes heart rate and blood pressure to rise so that the animal can prepare to either flight o fight. 
• Once the threat has passed, the parasympathetic branch of the ANS dampens down the stress response and the body goes back to nornal 

• HPA axis is triggered when the stress continues over a long time 
• H - hypothalamus releases CRH into the bloodstream 
• P - pituitary gland is affected by the CRH and causes it to produce ACTH into the bloodstream. 
• A - adrenal cortex is stimulated by ACTH and releases cortisol into the bloodstream, which lowers sensitivity to pain and gives a quick burst of energy, but als impares cognitive performance and if it is in the body for a long time can lead to immunosuppression and CHD. 

• Developed by Selye 
• He claimed that when animals are exposed to unpleasent stimuli, they display a universal response to all stressors. 
• He proposed there were 3 stages to GAS 
• Stage 1 : Alarm reaction - the threat is identified. The hypothalamus in the brain triggers the production of adrenaline/noradrenaline from the adrenal glands, which leads to the readiness for either fight or flight 
• Stage 2 : Resistance - if the stress continues, the body begins to adapt to the demands of the environment. But the body's resources are being depleated. The body appears to be coping, but it is actually deteriorating - the immune system becomes less effective. 
• stage 3 : Exhaustion - eventually the body can no longer maintain normal functioning. The initial symptoms of adrenaline may reappear. The adrenal glands may be damaged from over activity and the immune system may not work properly. This can result in stress related illnesses such as ulcers, depression and cardiovascular problems.

• Gender differences - it is suggested that males and females do not experience the same fight or flight responses. Females are more likely to experience the tend and befriend response. It is an evolutionary adaptation that means women do not run away or fight as they have to protect their young. Instead they protect their young (tend) and form alliances with other women (befriend). If they were to flee it puts the child at risk. The hormone oxytocin inhibits the fight or flight response. 
• Negative conseqences or fight or flight - fight or flight is most useful for situations where a lot of energy is required. But im modern life, most stressors do not need this level of energy. The stress respinse is repeatedly activated and can lead to damage to the body, such as CHD and immunosuppression. 

• Research support for gas - Selye's model was based on humans, and they all shared common symptoms such as aches and loss of appitite no matter what was wrong with them. He then investigated this with rats and found no matter what he injected them with they produced the same response. He gave them the common cold, surgical injury, cut their spinal cord. This showed that there are not different responses to stress and that the body response the same way to any stressor. 
• Stress-related illness may not be due to depletion of resources - more recent research shows that many resoucres (neurotransmitters, sugars) do not become depleated even under extreme stress, but that the exhaustion phase is linked to increased hormone activity, such as cortisol, and it is this rather than depletion that leads to stress related illnesses. 

• Research support for gas - Selye's model was based on humans, and they all shared common symptoms such as aches and loss of appitite no matter what was wrong with them. He then investigated this with rats and found no matter what he injected them with they produced the same response. He gave them the common cold, surgical injury, cut their spinal cord. This showed that there are not different responses to stress and that the body response the same way to any stressor. 
• Stress-related illness may not be due to depletion of resources - more recent research shows that many resoucres (neurotransmitters, sugars) do not become depleated even under extreme stress, but that the exhaustion phase is linked to increased hormone activity, such as cortisol, and it is this rather than depletion that leads to stress related illnesses. 

• Stress activates the sympathetic branch of the ANS, which leads to the production of adrenaline and noradrenaline 
• adrenaline causes: 
  • increased heart rate which takes its toll overtime 
  • constriction of blood vessels which increases blood pressure, causing tension on blood vessels
  • increased pressure can dislodge plaques on the walls of blood vessels and can lead t blocked arteries, which can cause a heart attack or stroke

• Williams et al conducted a study to see whether anger was linked to heart disease

Procedure - 13,000 people completed an anger scale, which included questions about whether they were hot headed, felt like hitting someone when they got angry. None of the p's had heart disease at the beginning of the sudy 

Findings - 6 years later, the health of the p;s were checked. 256 had experienced a heart attack, and people who scored high on the anger scale were 2.5 times more likely to have had a heart attack than people who scored low. This suggests SNS arousal is closely associated with cardiovascular disorders. 

• ongoing stress activates the HPA system, which results in the production of cortisol 
• one effect of cortisol is t reduce the body's immune respinse 
• this makes it more likely that a person will become ill. 

• Kieclot-Glasr conducted a natural experiment on whether the stress of exams affects the immune system 
• Procedure - 75 medical students took part in the study. Blood samples were taken a month before the exam (low stress) and during exams (high stress). Immune functioning was assessed by how many natural killer cells were in the blood samples. P's also compleated a questionnaire (SRRS) to measure stress they were experiencing. They also did a loneliness scale. 
• Findings - NK cell activity was reduced in the second blood sample, suggesting ongoing stress reduces immune functioning. Those who had high SRRS scores had lowest NK cell levels. P's with the fewest friends also had low levels of NK cells.

• Self report - most of the studies are based on self reports such as questionnaires. If someone has a tendency towards negative perceptions then they may exaggerate the unpleasent events, which makes a significant correlation more likely. 
• individual differences in cardiovascular effects - gender differences in the stress/immune system relationship. Women show more adverse hormonal and immunal changes in the way they react to conflict. Also as people age, stress has a larger effect on the immune system which makes it more difficult for the body to regulate itself. Sympathetic branch of the ANS is more reactive in some people (huperresponsive) meaning tha stress damages the body more
• stress does not always have negative effects on the immune system - sometimes stress can enhance the immune system. Up-regulation in short term stress, and down-regulation for chronic stress. Short term stressors promot the body to fight infection, however long term stress has detremental effects on the immune system 
•  not a simple relationship - Lazarus suggested that there are various ways why stress and illness is difficult to establish. 1. health is affected by many other factors such a genetics and lifestyle. 2. health is stable and slow to change, which makes it difficult to show that a particular stressor has an effect on someones health. 3. health needs to be measured for a long period of time to show the real effects of stress on health which is expensive and impracticle