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Aging and It's Effect on the Body

Biological Aging Theories

Summary: There are two main theories of aging 1. Primary Aging and 2. Secondary Aging. Both theories are workable models but the true reason is more likely a blending of the two.

There are two main theories to biological aging, They are known as Primary aging and Secondary Aging. Primary Aging is also known as Intrinsic Aging and is the aging caused by biological processes which cause physical declines. There are several theories to why primary aging occurs. There will be 2 discussed in this article. The first is Aging at the DNA level in the cells. This is thought to a pre-programmed or genetics controls our destiny theory. When and how fast we age is pre-controlled by our DNA, therefore longevity is a genetic trait. The fact of the matter is that cell duplication seems to be genetically programmed, or actually genetically doomed. Every time a cell divides it makes a copy of it's DNA for the new cell. Unfortunately no copy is ever perfect, and eventually the copy of the DNA is not viable. The current research suggests that a human cell can divide about 50 times +/- 10 times. There have been some research into re-invigorating cell DNA which has shown promise in extending the lifespan of human cells. The second theory of Primary Aging is that of Cumulative Effects of Random Events. Cell damage is inevitable in this modern world this damage does happen and is very slow to repair itself. One theory of why this cell damage takes so long to repair is the gradual slowing of human growth horomone which begins to slow in the 20's. This growth horomone is what regulates metabolism, enhances cell communication, and repairs the cells, etc. etc. Another way that cells are damaged is by a chemical process known as free radicals. These strong chemical reactions damage DNA and create chaos in the cells. The overall cell damage that is not repaired over time weakens organ systems, organ reserves (also known as the second wind) slows metabolism, and creates problems in homeostasis of the body, or its ability to bounce back and rebalance itself. Primary aging is most probably caused by a mixture of these 2 theories and not specifically one or the other.


Secondary Aging is also known as Extrinsic Aging. This is aging cause by environmental or disease processes that speeds up the actual aging process. It becomes more influential over time due to weakened organ systems and cellular functioning. Everyone has probably seen this in a relative or friend that gets sick and seems to age in front of you. Or that lady from Beverly Hills that suntans everyday and gets that leathery skin look by the time she is 40.

For more information on primary and secondary aging click here

All information in this Article came from Notes from 10-15-04 Psych 303 Adult Development and Aging. Taught by Dr. Gary Creasey PhD. Illinois State University.

This article contributed by Ben Clyde

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