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Nervous System
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The
major function of this system is to direct immediate responses to
stimuli by coordinating the activities of other systems.
The
aging process affects all body systems, and the nervous system is no
exception. Anatomical changes begin shortly after maturity (probably by
age 30) and accumulate over time. Although an estimated 85% of elderly
over the age of 65 lead relatively normal lives, there are noticeable
changes in mental performance and central nervous system (CNS)
functioning.
Some
common age-related anatomical changes in the nervous system include a
reduction in brain size and weight due primarily to a decrease in the
volume of the cerebral cortex. There is also a reduction in the number
of neurons.
Blood
flow to the brain is decreased as a result of fatty deposits that
gradually accumulate in the walls of blood vessels and reduce the rate
of arterial blood flow. This condition is called atherosclerosis and
causes problems in more than just the brain. While reduced blood flow
does not cause a cerebral crisis, it does increase the probability of
suffering a stroke.
There
are also changes in the synaptic organization of the brain which
ultimately interferes with the body’s ability to adjust to
internal and external stimuli. The number of dendrite branches and
interconnections decrease, while the rate of neurotransmitter
production declines. At the same time many neurons begin accumulating
abnormal intracellular deposits or plaques. There is evidence that when
these are present in excess, clinical abnormalities similar to
Alzheimer’s disease occur.
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Not
so fun fact:
Alzheimer’s
disease is a complex disease resulting from a combination of genetic
mutations, genetic susceptibility, and environmental factors. It is a
progressive disorder characterized by the loss of higher cerebral
function, and it is the most common cause of senile dementia, commonly
termed “senility.” The first symptoms usually
appear at 50-60 years of age. Alzheimer’s disease affects an
estimated 2 million people over the age of 65 in the US and causes
approximately 100,000 deaths each year.
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Fun
fact:
The
olfactory system, which is involved in the sense of smell, is very
sensitive. As few as four molecules of an odorous substance can
activate an olfactory receptor.
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These
anatomical changes are linked to a number of functional alterations. In
general, neural processing becomes less efficient. For example, memory
consolidation often becomes more difficult, and sensory systems of the
elderly, notably hearing, balance, vision, smell, and taste, become
less acute. Light must be brighter, sounds louder, and smells stronger
before they are perceived.
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