W4&5 - Stress ✅ Flashcards
What is stress?
- Stressor = a situation that ‘causes stress’ to a system (e.g. aversive event)
- Stress reactivity = the way we respond to a stressor.
-> Stressors (causes of stress) can be physical, psychological or social.
Effects of stress (temporarily & long-term)
Temporary:
- Changes in breathing: increased risk of asthma attack AND increased risk of panic attack
- Worsen existing mental health conditions
- Changes in eating behaviours
- Diarrhea/ constipation
Chronic/Long-term:
- Muscles of body – constant state of guardedness
- Tension-type headache/ migraines
- Long-term heart/ blood problems: hypertension and heart attack
Different pathways of the stress response?
- ‘HPA axis’: Hypothalamus -> Pituitary gland -> Adrenal gland
=> slower and in response to unexpected wounds - ‘Sympathomedullary pathway’: Hypothalamus -> Autonomic NS -> Adrenal medulla
=> provide short burst of energy
What is the role of Hypothalamus in stress response?
Hypothalamus:
- centrally located in the brain
- generally involved in homeostasis
-> study: stimulating hypothalamus can lead to undirected rage
=> involved in stress responses by releasing corticotropin (CRH)
What is the role of pituitary gland in stress response?
Located beneath the hypothalamus (‘master gland’)
Releases:
1. Somatotrophin (e.g. HGH, growth)
2 Thyrotrophin (TSH, metabolism)
3. Gonadotrophin (LH, FSH, fertility)
4. Corticotropin (ACTH -> stress)
What is the role of adrenal gland in stress response?
Location: on top of kidneys
Release a set of hormones involved in stress:
- Cortisol: in response to ACTH, metabolism, immune system suppression
- Epinephrine
What happens when there is too much/too little cortisol
Too much - Cushing’s syndrome
- Rapid weight gain
- Acne
- Reduced libido or infertility
- Thin skin
- Chronic tiredness
Too little - Addison’s disease
- Weight loss
- Weakness
- Adrenal crisis (low blood pressure, confusion/ psychosis, loss of consciousness) -> brought about by stressors
What is meant by Selye’s General Adaptation Syndrome (response stages to stressor) and features of each stage?
- Alarm - 1st encounter w stressors
- Arousal of the Autonomic NS
- Resistance to stressor drops below normal
- Adrenaline & cortisol hormones released into bloodstream
-> Sympathetic NS activated - Resistance - continuous exposure to stressor
- Parasympathetic system returns physiological functions to normal levels
- Remain high stress responses
-> Overtime resistance to stressor increases, levels out of normal levels (plateau)
=> Adapting to stressful environments - Exhaustion - if the stressor continues beyond body’s capacity
- Depletes available resources
- Loss of ability to adapt
- Susceptible to illness & death
What is meant by neurobiology of dread?
- 29 Ps underwent fMRI with electrical shock to foot but can choose the maximum voltage tolerable (100% voltage at start)
- Can either choose 90% voltage in 3s OR 60% voltage in 27s
- Some chose more voltage now than to wait
Results:
- More voltage = greater activation in pain network (show in fMRI scan)
Health Consequences of stress responses?
- Fatigue, diabetes (high blood glucose)
- Stress-induced hypertension (cardiovascular)
- Peptic ulcers (suppress digestion)
- Psychogenic dwarfism (suppress growth)
- Amenorrhea, impotency (suppress reproduction)
- Increased disease risk (suppress immune system) -> reduced B&T lymphocytes
- Neuron death (sharpen cognition) -> less dendrites form
What are the 4 psychological modifiers of stress response?
- Outlets for frustration
- Sense of predictability
- Perception of life improvement
- Social support
Evidence that supports these psychological modifiers for stress response? (example)
- Outlets for frustration:
- All rats received mild shock, prolonged period all developed ulcers
- Some rats that were allowed to eat and run on wheel -> fewer ulcers - Sense of predictability/control
- Rats hear warning bell before shock -> fewer ulcers
- Receive food at consistent intervals -> lower stress hormone in bloodstream
- Rats given a lever to avoid shock -> stress response is reduced
- Study with people in nursing home, group that was able to make choice -> 1.5yrs later more cheerful, active and alert - Sense of life improving
- Rats that receive fewer shocks on 2nd day -> less stress (even though no. of shocks is higher) - Social support
- Primates show lover cortisol levels when around friends than strangers
- People with spouse live longer -> higher mortality rate when spouse dies
Studies on the effect of prenatal stress?
Study on pregnancy during famine
-> change in metabolism of fetus (permanent shift)
=> good at storing consumed food and retaining salt from diet
Study on birthweight
-> lower birthweight = higher stress
=> early exposure to stress change stress reactivity
Study on pregnant rats
-> Rats born from mom with prenatal stress show freezing in bright light, have difficulty learning and greater anxiety, amygdalae have greater glucocorticoid receptors
How does the brain regulate perceived threat?
- ‘Bottom-up’ signaling from Amygdala -> indicate threats
- ‘Top-down’ regulation from medial pre-frontal cortex prevents triggering stress-responses
Stress effects on memory (+ encoding and retrieval)
- Memories tied to a stressor are better remembered.
- Normally adaptive BUT dysregulation could result in psychological trauma (e.g. PTSD)
Effects on encoding:
- Pre-learning: increase on cortisol, lowering hippocampus activity => better memory
- Post-learning: enhance consolidation for emotional pictures but not neutral ones
Effects at retrieval: Memory retrieval during stress is impaired
=> While encoding (& consolidating) better, retrieval is worse
