Stress

Current approach to defining stress emphasises individual differences; The transactional model. The key processes are primary appraisal + secondary appraisal

The neuron These make up the nervous system It can transmit elestrical pulses of electrical activity known as nerve impulses  which begin on the dendrites, travel along the cell body + along the axon. All aspects of human behaviour are coded by patterns of nerve impulses in different parts of the nervous system.

The synapse; is the gap between the axon terminals Transmission across the synapse is chemical Nerve impulses traveling down the axon stimulate the release of neurotransmitters into the synapse at the axon terminal They then bind to the receptors which alters the biochemical characteristic of the postsynaptic memebrane to make the nerve impulses more likely to be triggered However nerve impulses has an all or nothing principle, it either happens or it doesn't. If only a few impulses arrive the amount of neurotransmitters released will not be sufficient and the postsynaptic membrane will not fire. Synapses can be defined by the neurotransmitter they release.

The brain and the spinal cord make up the central nervous system (CNS) Radiating from the spinal cord are the spinal nerves which connect the organs with the CNS  Sensory info is carried in sensory pathways that run from the sensory receptors to the CNS, although visual + auditory sensory pathways don't involve the spinal cord. Motor pathways allow the brain to control movement + internal organs. spinal nerves contain sensory + motor pathways which make up the peripheral nervous system.

The autonomic nervous system (ANS) centres are located in the brainstem ANS pathways run down through the spinal cord + are distributed throughout the body by spinal nerves It is concerned with the regulation of our internal env. (body temp, heart rate + blood pressure) Eg homeostasis. It has 2 divisions; the sympathetic branch + the parasympathetic branch Nerve fibres from both branches connect with internal structures. Usually the 2 branches are balanced but if the sympathetic branch is dominant= patterns of bodily arousal + if the parasympathetic branch is dominant=opposite-biological calm These shifts are determined by the body's requirements

                                                                                      The brain              Hindbrain                                    Midbrain                                                           Forebrain (largest division)Medulla      Pons     Cerebellum                                               Cerebral hemisphere                                     Diencephalon                                                                                  Cortex     Basal ganglia    Limbic system         Thalamus     Hypothalamus

The medulla pons+midbrain are classified as the brainstem which contains the major autonomic centres. The thalamus is a sensory structure. The hypothalamus lies at the base of the brain. This controls the pituitary gland and the autonomic centres. Appraisal processes occur in the cortex+limbic system which stimulates the hypothalamus=HPA+SAM pathways. The limbic system includes the hippocampus, amygdala, septum +cingulate gyrus which are involved in functions such as learning memory and emotions. It has extensive connections to the hypothalamus and the cortex. The basal ganglia have functions in movement+motor control. The cerebral cortex contains within it the highest cognitive functions such as personality, consciosness, perception, etc. It is divided into 4 lobes; frontal parietal temporal+occipital.

Primary+secondary appraisal depend upon sensory processing systems and stored memory of previous encounters with the situation If the situation is percieved as stressful the hypothalamus is alerted.

The hypothalamic-pituitary-adrenal axisThe hypothalamus stimulates the release of ACTH from the pituitary gland. The hormone travels to the adrenal cortex which is part of the adrenal gland  to stimulate the release of corticosteroids such as cortisol.

The sympathetic-adrenomedullary pathwayAt the same time; Nerve pathways of the SNS runs to the adrenal medulla, the other part of the adrenal gland. When stimulated it releases the hormone adrenaline + noradrenaline.

These hormones are designed to provide for energy expenditure used in responses to stress Eg for escape

The SNS itself speeds up heart rate+ raises blood pressure. Adrenaline +noradrenaline increase+sustains these effects=oxygen is rapidly pumped to muscles to allow for increased activity.

Corticosteroids increases the release or mobilisation of energy stores such as glycogen=raised blood levels of glucose+fatty acids

Sustained raised levels of corticosteroids suppresses the immune system

These systems allow for energy expediture which makes sense when the stressor requires a physical response however now fast running isn't usually an effective coping response for certain stressors. In these cases the response to stress can lead to illness

Selye's general adaptation syndrome (GAS) He noticed that rats given repeated daily injections developed stress related syptomes such as gastric ulcers  He developed a 3 stage model of how the stress response; 1 Alarm stressor percieved, HPA+ SAM activated stress related hormones surge, heart rate+blood pressure increase+energy reserves are mobilised 2 Resistance If stressor persists response systems are maintained (hormones+bodily arousal) 3 Exhaustion Chronic stress exhausts the body's defense systems+it's ability to maintain high levels of hormones+bodily arousal.

Eval; influential in stress research He emphasised roles of HPA+SAM+links between chronic stress +illness He emphasised that the GAS was a common response to all stressors=ignores individual differences+cognitive elements This work was based on rats+a small amount of physical stressors It is now thought that stress related illnesses are not caused by exhaustion of the body's defenses, rather the effect of lasting raised levels of hormones

Types of stress; Segerstrom + Miller; acute time-limited stressors, brief naturalistic stressors + chronic stressors

Stress+physical illness; increased heart rate+blood pressure=damage to blood vessels/heart (eg atherosclerosis) Or stress=weakened immune system

The immune system is an immensely complex set of interacting processes that provides the body's defences against infection or illness from viruses and bacteria or infectious processes. It is made up of various cells and proteins. Immunodeficiency diseases such as AIDS involve destruction of the immune system. Autoimmune diseases cause the immune system to fail to recognise it's own body tissue and it attacks. Some forms of cancer are autoimmune diseases. Natural immunity involves phagocytes (or macrophages or NK cells) ingulfing and ingesting pathogens. It acts quickly+is our first defence. Specific immunity involve lymphocytes (T+B cells) that recognise pathogens+produce antibodies. Specific immunity is divided into cellular+humoral immunity. It develops over days. Cellular immunity involves T cells (killer+memory+helper). Humoral immunity involves B cells+the secretion of antibodies. The effect of stress may be general or it may affect natural more than specific or it may alter the balance between humoral+cellular.

 - Cohen et al. 1993 -

                           - Kiecolt-Glaser et al 1984 - The overall conclusion of these studies is that life stressors can all reduce immune function However they don't address some of the issues raised in the outline of the immune system such as the effect of different stressors on different parts of the immune system

Meta-review of stress research The effects of stress are influenced by many factors=each study is different However many may be in the general area Eg effects of stress on immune function Putting all data together =reliable Segerstrom+Miller 2004 293 studies that have looked at the effects of different stressors on measures on immune system functioning; Acute time-limited stressors; these lead to an upregulation of natural immunity Eg increase in no of NK cells Fast response to onset of stressorsBrief naturalistic stressors; no overall effect despite Kiecolt-Glaser's findings and evidence for a shift from cellular to humoral immunityChronic stressors; the most consistent effect; all measures of natural+specific immunity showed downregulation This was consistent across all age + gender groups Non-specific life events; They used a life event questionnaire (frequency+intensity of a range of life events) and found no overall significant change However for over 55's there was a relationship between life event stress+reductions in NK cell activity General conclusions;Acute stressors=increase in natural immunity Chronic stressors=reduction in immune function sometimes called global immunosuppressionAcute stressors=fight/fight stress response+Selye's GAS Rapid natural immunity prepares the body to fight off infection whereas specific immunity takes longer + is energy intensiveChronic stressors=changes become less adaptive + gloabl immunosuppression occurs Immune changes are simple No general evidence for gender differences However (Kiecolt-Glaser) women show greater reductions in immune function than men in marital conflict

Factors that should be considered when evaluating a study; what stressor was investigated? + how was it measured? was it acute or chronic? What indicator of immune function was measured? Were individual differences considered?

Chronic stress may lead to global immunosuppression because hormones released affect the immune system High levels of corticosteroids=reduce production of T cells + shrinkage of thymus gland

Life events may occasionally happen, which even if they are happy they can be stressful Eg christmas  Stress is a part of everyday life and can be minor or acute or severe or chronic but most people don't develop stress related illnesses.

Measuring stress;Self report questionnaires on frequency of life stress (in relation to life events or daily stressors) Self report questionnaires on percieved or subjective stress Eg how stressed do you feel?Semi-structured interviews P talks through their life stressors + trained interviewer assess the impact of the stressors (qualitative approach)These are used in certain areas such as the workplace

 - Holmes + Rahe 1967 -

In Holmes + Rahe's study death of a spouse was rated as the event that requires the most adjustment=most stressful Their scale is easy to use as you simply add up the LCU's for life events occuring in the previous yr Ascore over 150 is classified as a life crisis + according to Holmes + Rahe increases the chances of illness by 30% A score over 300 is a major crisis + increases the chance of illness by 50% Some of the studies of Holmes + Rahe were retrospective and they found suport for a relationship between LCU scores + stress related disease A prospective study is one in which the P's LCU units are assessed + then they are followed up to see if illness develops Eg                                                 - Rahe et al. -

The SRRS scale; It doesn't take into account the emotional impact of the event Holmes + Rahe assumed all events, regardless of their nature involved readjustment + were therefor stressful It doesn't take into account individual differences Each of us could construct a personal life event scale-each would be different Restrospective self report is unreliable due to exaggeration or forgetting or lying Results are usually in the form of correlations which don't imply cause

Therefor other scales have developed; The life event scale allows people to rate 57 life events in terms of severity of impact and whether the impact is positive or negative Which allows individual differences Specialised sections can be added Eg for students this produces 3 scores; negative change, positive change and total change In general, negative life event scores correlated more highly with illness outcomes

Lazarus felt hassles were more significant for health than major life events so he devised a hassle scale;The original scale had 117 items covering all aspects of daily life  though it could be modified for certain groups He felt that life also contained positive events-uplifts which counteract the negative effects of daily hassles An uplift scale was created with 135 positive items Scores on the hassles scale correlated with stress related problems (depression+anxiety) De longis et al 1982 did a study on both the hassle scale + a life event scale + found correlations with health outcomes were greater for the hassles scores Uplifts were unrelated to health outcomes

Background info

The body's response to stress

Stress in everdyday life