A lzheim er Disease
lzheimer disease (ALTZ-hT-mer) or (AD) is a disabling senile
dementia that results in the loss of reasoning, memory, and
the ability to care for oneself. Although AD can start as early as
age 30, 90%
of AD patients are over 65 years of age. The cause
seems to be a combination of aging and genetic, lifestyle, and
environmental factors. The disease begins with memory loss and
progresses to disorientation, personality changes, loss of cogni-
tion and recognition, and loss of language. Pathologically, the
disease is characterized by three changes:
Formation of amyloid plaques, made of
-amyloid protein
and bits of degenerated neurons
Loss of neurons associated with learning and memory
Formation of neurofibrillary tangles (NFT), abnormal bundles
of protein filaments inside neurons of affected brain regions,
as shown.
By the final stage of AD, the brain tissue has shrunk considerably.
Most patients with AD are dead within seven years of the onset
of symptoms.
Although the pathogenic mechanism for the disease is not
fully understood, recent studies have determined that individuals
with Type II diabetes are at least three times as likely to develop
Alzheimer disease as those who do not have diabetes. Research
studies have also isolated three genes involved in the process;
current research is focused on determining how the amyloid
p r o v id er
s e e s
plaques and NFTs form and identifying risk factors for AD. Medi-
cal therapies have not been entirely effective in slowing the pro-
gression of the disease, and no therapies are available to repair
damage that has already occurred in these patients.
Prevention appears to be the best “medicine" for Alzheim-
er's disease. Preventive activities include eating a diet rich in
fruits, vegetables, grains, olive oil, fish, and red wine; doing
regular physical activity; and engaging in intellectual activities
such as working crossword puzzles, reading, playing games, and
interacting with others. Regular participation in these types of
activities can reduce the risk of developing AD or will at least
delay the onset of the condition.
Very early stage AD
Mild to moderate stage AD
Final stage (severe) AD
Think Critically»
A D is associated with loss of m em ory
and cognition. W hich part of the brain is m ost affected?
H ow w ould advanced A D affect m otor skills such as w rit-
ing? Explain your answer. In your explanation, refer to the
neural pathw ays involved.
In the cerebrum, the sensory and motor areas have
groups of neurons devoted to specific parts of the body
(mouth, hands, feet, visual fields, auditory fields, and
so on). Essentially, these areas have “maps” of the body
wired into them. Figure 7.11 shows the maps called ho-
munculi (singular is
h o m u n c u lu s)
of the primary somato-
sensory area and the primary motor area of the body.
Although the maps appear distorted, they show that ar-
The Nervous System
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