Sapolsky, Chapter 12 Aging and Death

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Sapolsky, Chapter 12Aging and Death
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Aging is a relatively new phenomenon.

• Only recently in evolutionary terms, did we have
  the luxury of old age, especially fairly healthy
  old age.
• Some twenty percent of all humans who have ever
  lived past the age of 65 are now alive.

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Quest for youth
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Changes with age

• East Africa Elders are honored.
• USA aging is not so bad in many cases.
• Size of social networks shrink quality may
  improve.
• Social intelligence strategic use of
  information increases memory of facts declines.
• Average happiness increases
• Apparent in imaging studies and in
  questionnaires.

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Aged organisms and stress

• In absence of stress, young and old perform
  similarly. With stress, greater decline in old
  people and animals.
• Difficulty both turning on and turning off stress
  responses.

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Failure to activate sufficient stress response

• Cellular responses
• Heat shock proteins
• DNA repair enzymes
• Antioxidant enzymes
• Exercise
• Less cardiac work capacity
• Less response to epi. norepi.

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Failure to activate sufficient stress response

• Decrease blood to brain
• Energy levels decline faster
• Temperature stress
• Longer to restore normal temperature
• Cognition
• Similar to young except in timed tests

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Too much stress response

• Too long to turn off stress hormone response
• Higher resting levels of stress hormones
• Price of high GCs
• Hippocampus neurons die ? impaired memory
• Also ? less negative feedback on GCs
• Decrease GCs ? neurogenesis is restored.

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Location of hippocampus
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Why you seldom see really old salmon

• Programmed die-off after spawning in
• salmon and male marsupial mice.
• Due to excessively high GC, with all the
  stress-related disorders.
• Huge adrenal glands
• Peptic ulcers
• Immune systems collapsed
• Teeming with parasites infections
• Take out adrenals ? live for another year.

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Chronic stress the aging process in the
mainstream

• Max Rubner
• Only so much metabolism before mechanisms of life
  wear out.
• Rat (400 heart beats/minute) uses up allotment
  faster than elephant (35 beats/minute)
• Not true in strict interpretation
• Not true at all within species

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Wear and tear hypothesis

• Prolonged high stress hormones ?
• Type 2 diabetes
• Hypertension
• Cardiovascular disease
• Osteoporosis
• Reproductive decline
• Immune suppression
• Since high stress hormones are common in aging,
  they may account for some of these disorders in
  older people.

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Is everything lost???

• No!!
• Some humans, monkeys, and rats age successfully.
• Topic of Sapolskys last chapter.

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Main points

• Good and bad aspects of aging
• Bad aspects seen mostly under stress
• Problems too little or too much stress response
• Increased GCs can cause a lot of problems
• High GCs can kill salmon and male marsupial mice.
• Negative feedback on GCs (hippocampus) is
  decreased by high levels of GCs (vicious circle)