Since research into aging is not guided by any one universally accepted theory,
genetic, cellular, and physiological studies have yielded several hypotheses.
Genetics The most popular genetic theory, the Error Theory, assumes that aging
is the result of the accumulation of random genetic damage, or from small errors
in the flow of genetic information. The damage or errors would reduce or prevent
proper cell function. Cellular The best known theory of aging in cellular
research is called the Hayflick Effect, which is named after the American
microbiologist Leonard Hayflick. He found that certain human cells could only
divide a limited number of times before they die. This may suggest that aging is
"programmed" into cells. This could also account for the differences
in the life spans of different animal species, and the differences in the life
spans between the sexes within the same species. Physiological These theories
focus on organ systems and their interrelationships. One area currently being
investigated is the immune system. As we age the immune system gradually loses
its capacity to fight off infections and other invaders. As a result, antibodies
are produced that cannot tell the difference between "friendly" cells
and "enemy" cells. Most experts now believe that aging represents many
phenomena working together (Miller and Keane 97). PHYSICAL CHANGES The physical
changes that accompany aging are not necessarily incapacitating, even though
they may be discomforting or limiting. The body has less strength and endurance
as it ages. The rate of energy production in the body cells is gradually lowered
so that people tire more easily and are more sensitive to weather changes.
Sexual desire and ability lower although they never entirely end for either sex.
The capacity to bear children ends in women with menopause, which is the time
when the ovaries stop functioning, causing the menstrual cycle to stop. Men
retain their reproductive function into the late years. The use of eyeglasses
may become necessary, even if they were not necessary earlier in life. Old
people can hear low tones fairly well, but their ability to hear high tones
decreases. The capacity of tissue and bone to repair itself is slowed, as is
cellular growth and division. Bones become brittle and skin loses its thickness
and elasticity, causing wrinkles. As brain cells die some capacity for
memorization and learning is lost. Breathing becomes difficult and hardening
arteries circulation to worsen and blood pressure to rise. Joints lose their
mobility and deteriorate from constant wear and pressure. Finally, the liver
filters toxins from the blood less efficiently (Microsoft Encarta
"Aging"). These are not all of the changes to the body that are
brought about by aging, but these are the major ones. There is hope in modern
medicine, though. Through the use of new technologies and drugs some of these
changes can be slowed or prevented. System Results of Aging Contributing Factors
SKIN -loses thickness and elasticity (wrinkles appear) -bruises more easily as
blood vessels near surface weakens -Process accelerated by smoking, -excessive
exposure to sun. BRAIN/NERVOUS SYSTEM -loses some capacity for memorization and
learning as cells die -becomes slower to respond to stimuli (reflexes dull)
-Process accelerated by overuse of alcohol and other drugs, repeated blows to
the head. SENSES -becomes less sharp with the loss of nerve cells -Process
accelerated by smoking, -repeated exposure to loud noise. LUNGS -becomes less
effective as elasticity decreases -Process accelerated by smoking, -poor air
quality, insufficient exercise. HEART -pumps less efficiently, making exercise
more difficult -Process accelerated by overuse of alcohol and tobacco, poor
eating habits. CIRCULATION -worsens and blood pressure rises, as arteries harden
-Process accelerated by insufficient exercise, smoking, poor eating habits.
JOINTS -lose mobility (knee, hip) and deteriorate from constant wear and
pressure (disappearance of cartilage between vertebrae results in old age
"shrinking") -Process accelerated by injury, obesity. MUSCLES -lose
bulk and strength -Process accelerated by insufficient exercise, starvation.
LIVER -filters toxins from blood less efficiently -Process accelerated by
alcohol abuse, viral infection. Microsoft Encarta. "Aging." MENTAL
CHANGES Along with the loss of the ability of memorization and learning due to
brain cells dying (Microsoft Encarta "Aging"); elderly people can be
affected by Alzheimer's Disease. This disease is a progressive degenerative
disease of the brain, now considered to be a leading cause of dementia among the
old. It affects an estimated 2.5 to 3 million people in the U.S. The incidence
of this disease increases with advancing age, but there is no evidence that it
is caused by the aging process. The average life expectancy of a person with
Alzheimer's is five to ten years. Alzheimer's patients show nerve cell loss in
the parts of the brain associated with cognitive functioning. The disease also
includes the formation of abnormal proteins known as neurofibillary tangles and
neurotic plaques. Alzheimer's is also identified by defects in the brain's
neurotransmitters, chemicals that transmit nerve impulses, particularly
acetylcholine, which has been linked with memory function. Recent findings show
that a small percentage of Alzheimer's cases may have been inherited, and there
has been a link between the disease and high amounts of aluminum in the brain
(Microsoft Encarta "Alzheimer's Disease"). Senile Dementia This form
of intellectual impairment is observed in elderly people. Approximately 10
percent of all people over 65 years of age have clinically important
intellectual impairment. Although 20 percent of these cases are treatable, such
as toxic drug reactions, most cases are Alzheimer's Disease. Senile Dementia
begins with failing attention and memory, loss of mathematical ability,
irritability and loss of sense of humor, and poor orientation in space and time
(Microsoft Encarta "Senile Dementia"). CONCLUSIONS 1. There is no one
theory about why we age, but the subject is currently being researched in
several areas. 2. The body goes through many changes as it ages, some of which
can be slowed or prevented through the use of modern medicine. 3. Alzheimer's
Disease is probably the most prominent mental disorder in elderly people, but
research has found what it does to the brain, so a cure may be in the
future.BibliographyMicrosoft Encarta. Computer Software. "Alzheimer's Disease."
Microsoft, 1993. Computer Software. "Senile Dementia." Microsoft,
1993. Miller, Benjamin F., M.D., and Claire Brackman Keane, RN, BS, M.Ed.
Encyclopedia and Dictionary of Medicine and Nursing. USA: W. B. Saunders, 1972.
Riley, Matilda White. "Aging." Microsoft Encarta. Computer Software.
Microsoft, 1993.