Physiological Stress Responses Short term stress response n

Physiological Stress Responses Short term stress response n n The HPAA The fight/flight response Long term stress response n The general adaptation syndrome

Selye and GAS (1956) General it refers to the belief that there is the same general bodily response to all stressors. Adaptation refers to his view that the stressor response enables organisms to adapt to stressors Syndrome means that typical or characteristic combination of factors that make up the stress response

General Adaptation Selye (1936) Rats exposed to a variety of severe but non-lethal stressors Exercise, injury, mutilation, poisoning n A long-term response to stress was observed that was independent of stressor type n

Selye’s work on rats Selye put rats in unpleasant situations such as having injections, extreme cold and having limbs cut off. He measured there physical stress response and they all responded in the same way. Hence his GAS theory. He split his theory into 3 stages

Stage 1 - Alarm reaction Threat or stressor is recognised the stress response is elicited. The SAM system goes into action releasing Adrenaline There is some activation of HPA axis, producing cortisol.

Stage 2 Resistance If stress continues, the body needs to find some way of coping. If the body cannot cope there maybe outward normal appearance but there may be long term changes to the immune system because to the release of cortisol which causes the immune system to be less responsive.

Stage 3 Exhaustion Body can no long maintain normal functioning The initial SAM symptoms reappear The Peripheral nervous system functions at an abnormally low level an collapse of the body’s immune system. Also how people die of shock. Results in stress related illness such as high blood pressure, asthma and heart disease.

General Adaptation Syndrome recap Alarm n n Immediate response to stressor Fight or flight Resistance n n n Body tries to adapt to stressor Hormonal changes to cope with stress Conservation of resources Effects on activity level, feeding etc. Not necessarily harmful

General Adaptation Exhaustion n Total depletion of coping resources n Metabolic changes n Decline in immune functioning n Increased susceptibility to infection

General Adaptation Adrenal Glands become enlarged Thymus shrinks Stomach develops ulcers

Evaluating GAS Ethical objections to use of animals n n Deliberate infliction of pain & stress Could alternative methods have been used? Problems generalising n n Rat and human physiology have similarities and differences Human stress is mediated by psychological factors

Evaluation Strengths Based on careful observation Large amount of research Identified link between psychological factors and physical illness

Evaluation - Weaknesses Ignores individual – i. e. interpretation of what a stressor is and ability to cope Work done on rats therefore cannot be generalised to humans He claimed that all stressors produce the same physiological response. However evidence suggests that there are specific responses to specific stressors (Cox) anxiety more adrenalin and aggression more noradrenalin.