PYC 4805:
Developmental
Psychology
Chapter 3
, 1. Why do We Age? Biological Theories of Aging
1.1. Metabolic Theories:
» One theory of aging that makes apparent common-sense postulates that organisms have only so much en
expend in a lifetime.
- Couch potatoes might like this theory and may use it as a reason why they are not physically active.
» The basic idea is that the rate of a creature's metabolism is related to how long it lives.
» Several changes in the way that hormones are produced and used in the human body have been associate
but none have provided a definitive explanation.
» Although some research indicates that significantly reducing the number of calories animals and people e
increase longevity, research focusing on nonhuman primates shows that longer lives do not always result f
restricting calories alone.
» Furthermore, the quality of life that would result for people on such a diet raises questions about how goo
calorie restriction is.
- That's because the calorie Chris tractions in this research tend to be extreme.
» Extrapolated to people, the restrictions could well cause a drop in humans’ ability to engage in the kinds o
would consider important for a high quality of life.
, 1.2. Cellular Theories:
» A second family of ideas points to causes of aging at the cellular level.
» One notion focuses on the number of times cells can divide, which presumably limits the lifespan of a com
Organism.
» Cells grown in laboratory culture dishes under girl only a fixed number of divisions before dying, with the n
possible divisions dropping depending on the age of the donor Organism ; This phenomenon is called the
after its discoverer, Leonard Hayflick.
- It turns out that the Hayflick limit sets an upper bound on the number of cell divisions possible even in th
other factors, such as telomere damage.
» What causes cells to limit their number of divisions?
- Evidence suggests that the tips of the chromosomes, called telomeres , play a major role in aging by adju
response to stress and growth stimulation based on cell divisions and DNA damage, and by typically short
each cell replication.
» An enzyme called telomerase is needed in DNA replication to fully reproduce the telomeres when cells div
- But telomerase Normally is not present in somatic cells, so with each replication the telomeres become s
- Eventually, the chromosomes become unstable and cannot replicate because the telomeres become too
» Chronic stress may accelerate the changes that occur in telomeres and thereby shorten one's life span.
- Research also shows that moderate levels of exercise may maintain telomere length or at least slow the r
telomeres shorten, which may help slow the aging process itself.
Developmental
Psychology
Chapter 3
, 1. Why do We Age? Biological Theories of Aging
1.1. Metabolic Theories:
» One theory of aging that makes apparent common-sense postulates that organisms have only so much en
expend in a lifetime.
- Couch potatoes might like this theory and may use it as a reason why they are not physically active.
» The basic idea is that the rate of a creature's metabolism is related to how long it lives.
» Several changes in the way that hormones are produced and used in the human body have been associate
but none have provided a definitive explanation.
» Although some research indicates that significantly reducing the number of calories animals and people e
increase longevity, research focusing on nonhuman primates shows that longer lives do not always result f
restricting calories alone.
» Furthermore, the quality of life that would result for people on such a diet raises questions about how goo
calorie restriction is.
- That's because the calorie Chris tractions in this research tend to be extreme.
» Extrapolated to people, the restrictions could well cause a drop in humans’ ability to engage in the kinds o
would consider important for a high quality of life.
, 1.2. Cellular Theories:
» A second family of ideas points to causes of aging at the cellular level.
» One notion focuses on the number of times cells can divide, which presumably limits the lifespan of a com
Organism.
» Cells grown in laboratory culture dishes under girl only a fixed number of divisions before dying, with the n
possible divisions dropping depending on the age of the donor Organism ; This phenomenon is called the
after its discoverer, Leonard Hayflick.
- It turns out that the Hayflick limit sets an upper bound on the number of cell divisions possible even in th
other factors, such as telomere damage.
» What causes cells to limit their number of divisions?
- Evidence suggests that the tips of the chromosomes, called telomeres , play a major role in aging by adju
response to stress and growth stimulation based on cell divisions and DNA damage, and by typically short
each cell replication.
» An enzyme called telomerase is needed in DNA replication to fully reproduce the telomeres when cells div
- But telomerase Normally is not present in somatic cells, so with each replication the telomeres become s
- Eventually, the chromosomes become unstable and cannot replicate because the telomeres become too
» Chronic stress may accelerate the changes that occur in telomeres and thereby shorten one's life span.
- Research also shows that moderate levels of exercise may maintain telomere length or at least slow the r
telomeres shorten, which may help slow the aging process itself.
