Stress and Aging
All cellular stress-responses — heat shock proteins, DNA repair enzymes, antioxidant enzymes — become less responsive to challenge during aging. (Location 4007)
==Older individuals are impaired at turning off Epinephrine, norepinephrine, or Glucocorticoids secretion after a stressor has finished==; it takes longer for levels of these substances to return to baseline. Moreover, even in the absence of the stressor, epinephrine, norepinephrine, and glucocorticoid levels are typically elevated in aged rats, nonhuman primates, and humans. (Location 4024)
When salmon spawn, regulation of their glucocorticoid secretion breaks down. Basically, the brain loses its ability to measure accurately the quantities of circulating hormones and keeps sending a signal to the adrenals to secrete more of them. Take a salmon right after spawning, remove its adrenals, and it will live for a year afterward. If you want to degenerate very fast, secrete a ton of glucocorticoids. (Location 4051)
Most hormonal systems work by feedback-inhibition: the brain senses circulating glucocorticoid levels against a “set point.” If levels are low, the brain keeps secreting CRH. Once levels reach the set point, a negative feedback signal stops CRH secretion. This feedback regulation becomes impaired in old age — dexamethasone resistance. (Location 4083)
⇒ Your Brain, The Real Master Gland
The Hippocampus is one of the important negative feedback sites for controlling Glucocorticoids secretion. When the hippocampus is damaged, the rat secretes more glucocorticoids. Which should damage the hippocampus further — a degenerative feed-forward cascade. (Location 4101)
⇒ Stress and Memory
A subset of old rats had normal glucocorticoid levels basally and after stress. Their hippocampi had not lost neurons or receptors for glucocorticoids. All those awful degenerative features turned out not to be an inevitable part of the aging process. All those rats had to do was age successfully. (Location 6310)
If neonatal handling decreases the amount of glucocorticoids secreted as an adult, and such secretion in an adult influences the rate of hippocampal degeneration in old age, then handling a rat in the first few weeks of its life should alter the way it ages years later. And it does. (Location 6316)
Male baboons who in their prime spent lots of time affiliated with females, grooming, sitting in contact, playing with kids — they continue the same pattern for the rest of their lives. They get hassled by the current rulers, but it doesn’t seem to count as much as the social connectedness. ==That seems like a pretty good definition of successful aging for any primate.== (Location 6423)
When it comes to humans who wish to cope with stress and achieve successful aging, you should be sure to pick the right parents’ genes, and the right parents’ socioeconomic status as well. (Location 6432)
Winning an Oscar at any point in your life extends your life expectancy about four years, relative to actors who were nominated but didn’t win. (Location 10857)
see also
Tags: neurobiology science
Superlink: 051 ☣Neurobiology 050 🧠Neuroscience
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Erstellt: 05-04-26 10:00