08 Stress Flashcards
general adaptation syndrom (Seyle)
- stress is the nonspecific response of the body to any demand
3-stage model - alarm: fight-flight response, immediately after stressor appearance, immediate physiological response
- resistance: keeping initial response under control
- exhaustion: either exhaustion or recovery, if it can deal with it
What is a stressor, a stress response and stress
- stressor: stress-eliciting stimulus
- stress response: behavioral and physiological response
- stress: interaction between both
Lazarus’ transactional model of stress
- primary appraisal: interpretation of stimulus as positive, dangerous or irrelevant
- if dangerous, secondary appraisal: analysis of available resources, sufficient or insufficient
- if insufficient, stress elicited
- coping: overcoming of the stress, problem-focused (change situation) or emotion-focused (change the relation)
short-term stress response of ANS
- hypothalamus sends nerve impulses down the spinal cord via preganglionic sympathetic fibers to adrenal medulla which secretes adrenalin and noradrenalin
sympathetic vs. parasympathetic ANS
- sympathetic: fight-or-flight response
- parasympathetic: rest-and-digest
long-term stress response
hypothalamic-pituitary-adrenal (HPA) axis
- hypothalamus sends CRH (corticotropin-releasing hormones) to corticotropic cells in pituitary which release ACTH (adrenocorticotropic hormones) into blood stream
- transported to adrenal cortex which secretes steroid hormones and cortisol (mineralocorticoids and glucocorticoids)
- cortisol crosses BBB and closes feedback loop
function of HPA axis
- delay of +30min to hours after stress
- permissive, suppressive, stimulatory and preparative actions
- regulatory system: controls normal defense reaction
mineralocorticoid receptors
- mechanism: rapid nongenomic increase in glutamate release probability
- timeframe/delay: minutes
- hormonal dependence: shortly after stress, as long as corticosterone is high
- functional relevance: enhanced brain activity in specific limbic areas, acquisition strategy, activation, appraisal of the situation and/or for response selection, encoding and memory of the situation for future use
glucocorticoid receptors
- mechanism: slow transcriptional regulation of multiple genes
- timeframe/delay: hours
- hormonal dependence: some hours after stress, when corticosterone is low again
- functional relevance: normalization of brain activity, preservation of encoded information, storage for future use, recovery, redistribution of resources towards cortical networks, consolidation of memory and behavioral adaptation, prevents initial reaction from overshooting
psychological effects of stress
- enhanced consolidation of memory processing
- impaired retrieval of memory
- especially for emotionally arousing information
- executive functions: impaired working memory and cognitive flexibility
- shift from goal-directed to habitual control of action
- riskier decision making with focus on immediate rewards
- increased prosocial behavior and in-group bias, especially in women
stress measurements
- physiological: blood pressure, heart rate, electrodermal activity
- measurements of stress hormone concentrations (blood, saliva, hair)
chronic stress - effects of unbalanced glucocorticoids
too much glucocorticoids (anti-inflammatory):
- more infections
- lower efficacy of vaccination
- slower wound healing
- faster cancer progression
- faster aging
too little glucocorticoids (inflammatory):
- more autoimmune disease
- more inflammation
- more pain
chronic stress: neuroscientific findings
amygdala
- persistent dendritic growth and spine formation leading to hyper-responsiveness and symptom severity
hippocampus
- reversible dendritic atrophy and reduced neurogenesis leading to reduced volume and inverted correlation with symptom severity
medial PFC
- reversible dendritic atrophy and spine loss leading to hypo-responsiveness and inverted correlation with symptom severity
HPA axis in MDD
- enhanced basal and stimulated cortisol release, high CRF in CSF, exaggerated ACTH response to CRF, impaired negative feedback of HPA axis
- interpreted as reflecting an exaggerated CRF drive and/or as a reduction of functioning of GRs
