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What did Hans Selye do?
- Identified “general adaptation syndrome”, which he later renamed the “stress response”
- This constituted enlarged adrenal glands and lymph node and thymic atrophygastric erosions/ulcers.
- First to suggest that hormones from the adrenal cortex might be important, in addition to the already-known-about hormones from the adrenal medulla

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What are the two stress systems?
- The sympathetic-adrenomedullary system
- The hypothalamic-pituitary-adrenocortical system
- Basically sympathetic and parasympathetic response
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What are the features of the sympathetic adreno-medullary system?
- Fight or flight response (mostly flight)
- Focussed in the thoracic and lumbar parts of the spinal cord
- Readies us for danger
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What are the features of the parasympathetic response?
- Rest and digest
- Mainly focussed in the cranial and sacral regions of the spinal cord
- Maintains bodily function
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What are the features of the hypothalmic-pituitary-adrenocortical system
- In response to stress, Corticotropin releasing factor initiates a cascade of events that culminate in the release of glucocorticoids from the adrenal cortex
- These are Cortisol (hydrocortisone) in humans and corticosterone in rats
- Both are produced by the adrenal cortex
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What is the process of cortisol production?
- Corticotrophin releasing factor is produced in the hypothalmus
- This reaches the anterior pituitary, which stimulates the release of adrenocorticotrophic hormone, which travels to the adrenal cortex
- This produces cortisol and other hormones, which travel to target hormones to produce the stress response
- Some also travels back to the anterior pituitary (stimulating more release) and the hypothalmus (inhibiting release)
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What effects does prolonged exposure to cortisol have?
- Hippocampal shrivelling
- Ulcers to the hippocampus is associated with prolonged, and fatal stress in primates
- Smaller hippocampus heads found in PTSD Gulf war vets
- Impairs declarative function in healthy humans
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What effects does one's upbringing have on stress hormone production?
- Neglected monkies show higher plasma adrenocorticotrophic hormone levels, and an increased response to stress both in cortisol production, and its genetic manifestation, with more RNA receptor messengers for cortisol
- Same findings for women with a history of child abuse
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How is upbringing linked to epigenetics?
- Epigenetic means heritable effects that don’t alter the DNA sequence, and environmental factors that modify gene functioning
- Offspring of attentive mother mice have increased serotonin production, and demethylation of gene Nr3c1
- This is a promoter (activator) for another gene called NGF1-A, which regulates glucocorticoid activity (more is produced now)
- This is heritable because the offsprings’ own parenting will be affected in turn, and yet no DNA sequence was re-ordered
- This has been found in abused humans, with less demethylation, meaning stress responses can't be inhibited as easily. And this is linked to suicide..
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What long term effects can stress have?
- Cognitive decline in rats
- Limited nesting behaviour, worse nursing behaviour, struggles bringing up pups
- Worse at spatial learning
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