Stress Flashcards
what is stress?
Situation that upsets an animal’s homeostatic balance
what is a stressor?
Thing that causes stress
what neuroendocrine protection systems are activated in stress?
sympatho-adrenergic system (SAS)
hypothalamic–pituitary–adrenal (HPA) axis
Together these systems orchestrate response to potentially harmful or even life-threatening situations
Involves bi-directional brain–body communication
stages of the stress response
- alarm reaction
- resistance stage
- exhaustion stage
alarm reaction
stressor is perceived by pituitary–adrenal system
SAS system prepares body for action: “fight or flight”
HPA system releases energy stores
Prompted by sudden, unexpected appearance of stressor
Non-specific immediate behavioural response: startle
Followed by specific behavioural responses (fight or flight)
Primarily linked to stimulation of sympatho-adrenergic system (SAS)
resistance stage
body attempts to re-establish physiological balance
if stressor persists, stress hormones and arousal remain high
If stressor is handled successfully, body restores homeostasis and feedback loops return stress hormones to ‘baseline’ levels (recovery)
May see reduced impact of stressor with repeated exposures
exhaustion stage
prolonged stress eventually depletes resources and exhausts body’s defences
stress-related illnesses develop
what phys changes accompany the alarm reaction?
increase in blood pressure
tachycardia (rapid heart rate)
tachypnoea (rapid breathing)
These are active coping mechanisms for controlling the threat
what does the alarm reaction activate?
brainstem nuclei
vagal nerve
adrenal medulla - releases adrenaline and noradrenaline into blood
noradrenaline
stimulates alpha receptors in muscle; contraction redirects blood to essential organs and increases blood pressure
adrenaline
has wider range of effects
raises heart rate
increases blood flow to muscles
reduces blood flow to skin and intestines
stimulates glycogenolysis by liverglycogen broken down to glucose → raises blood sugar
causes adipose tissue to release fat into the blood
widens bronchioles (air passageways in lung)
dilates pupils
assists body to escape from/deal with stressful situ
what else is the alarm reaction accompanied by?
Accompanied by activation of hypothalamic–pituitary–adrenal (HPA) axis
ACTH stimulates adrenal cortex to release cortisol and other steroids
Engages slower-acting, passive coping mechanismsuseful when fight/flight is ineffective
adaptive redirection of energy in the alarm reaction
direct oxygen and nutrients to the brain
stimulates lipolysis breakdown of fats
stimulates gluconeogenesis production of glucose
inhibits growth and reproduction
suppresses immune system
contains inflammatory responses
enhances arousal, vigilance and cognition
what does severe, uncontrollable and long-lasting aversive events lead to?
sustained activation of the HPA axis
→ chronic stress
factors associated with the exhaustion stage
sugars are mobilised and energy is never stored - muscle wasting, fatigue, increased risk of diabetes
hypertension (high blood pressure) is maintained - damage to blood vessels
digestion is suppressed - peptic ulcers, irritable bowel syndrome
growth is suppressed - psychogenic dwarfism, bone decalcification
reproduction is suppressed - disrupted ovulation, impotence, loss of libido
immunity and inflammation are suppressed - long-term immunosuppression, increased disease susceptibility
cognition and sensory thresholds are altered - neural degeneration in hippocampus and pre-frontal cortex; impaired learning and memory retrieval
what causes stress?
Any stimulus can be a stressor if it is perceived to threaten homeostasis and activates the HPA axis
Most naturally occurring stressors involve a combination of both factors
systemic stressors
(actual threats)
visceral nociceptors
somatic nociceptors
inflammatory signals
stimulation of baroreceptors or osmoreceptors
neurogenic stressors
(anticipated threats)
lead to HPA activation in the absence of physiological challenge
anticipation/recognition of predators
dangers associated with novel environment
example of interactions with conspecifics
e.g. dominance interactions in baboons Sapolsky (2005)
dominant male’s testosterone recovers more rapidly after stressful event
subordinate males display higher levels of circulating cortisol
Dominance behaviour often subtle—threats rather than direct aggression
example of other subtle stressors
e.g. begging by meerkat pups Carlson et al. (2006)
adults’ long-term contributions to pup feeding are positively correlated with plasma levels of cortisol
pup begging both increases plasma cortisol levels and increases pup feeding by male helpers
modern env stressors
leading to high rates of chronic stress
job-related- high pressure, long hours, inconvenient shifts
financial worries
transport- traffic jams, dangerous driving, public transport
eustress
perturbation can be dealt with effectively; (beneficial) stress response quickly terminated once homeostasis restored
distress
chronic hypo-/hyperactivation of HPA axis; may be harmful and lead to abnormal behaviour
what tips the balance between eustress and distress?
Quality and intensity of the stressor
Characteristics of individual challenged by the stressor
- genetic predisposition
- past history/experience
- age or stage of development
Interpretation of stimuli varies between and within individuals and may be associated with emotional state (e.g. anxiety, arousal)
Yerkes-Dodson law
arousal improves performance up to an optimal point
past this point, performance begins to decrease
precise pattern is task-dependent
Lazarus’s transactional theory
Dynamic relationship between
- environmental demands (stressors)
- individual’s psychological resources for dealing with them (coping ability)
A stress response results from a perceived imbalance between these demands and resources
what was the beginning of modern research on stress?
combat stress in WWII veterans
Lazarus & Folkman (1984)
forms of cognitive appraisal
primary
secondary
primary appraisal
significance in terms of personal goals, values, self-beliefs
secondary appraisal
ability to control situation and importance for wellbeing
what does appraisal involve taking into account?
personal factors—goals, personal resources, beliefs about oneself and the world
situational factors—demands, constraints, opportunities and culture
problem-focused strategies
attempts to modify the situation that is causing the stress response
planning
delegating responsibilities
emotion-focused strategies
attempts to regulate the emotional response
seeking social support
stopping stressful thoughts
rationalising
avoiding
engaging in distracting tasks
stress immunisation example
e.g. handling of rat pups - Levine et al. (1967), Liu et al. (1997), Mirescu et al. (2004)
handling by humans is a mildly stressful event for rat pups
pups handled early in life secrete lower cortisol amountsin response to range of stressful events as adults
after handling, pups are licked more by their mothers
offspring of mothers who exhibit higher groomingand licking rates are more resilient to stress as adults
pups deprived of mothers for long periods show elevated stress,associated with changes in adrenal steroid receptors in brain
