Page 174 - 86 human physiology part-2

Development: Birth Through Death

of the aged are: change in activity level, reduced nerve supply to muscle, cardiovascular disease,
and nutritional deficienies.

Nervous System

One of the effects of aging on the nervous system is the loss of neurons. By the age of 30, the brain
begins to lose thousands of neurons each day. The cerebral cortex can lose as much as 45% of its cells
and the brain can wiegh 7% less than in the prime of our lives. Associated with the loss of neurons
comes a decreased capacity to send nerve impulses to and from the brain. Because of this the
processing of information slows down. In addition the voluntary motor movement's slow down, reflex
time increases, and conduction velocity decreases. Parkinson's diesease is the most common movement
disorder of the nervous system. As we age there are some degenerative changes along with some
disease's involving the sense organ's that can alter vision, touch, smell, and taste. Loss of hearingis also
assocated with aging. It is usally the result of change's in important structures of the inner ear.

Alzheimers disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive
deterioration together with declining activities of daily living and neuropsychiatric symptoms or
behavioral changes. It is the most common cause of dementia. The most striking early symptom is short
term memory loss (amnesia), which usually manifests as minor forgetfulness that becomes steadily
more pronounced with illness progression, with relative preservation of older memories. As the
disorder progresses, cognitive (intellectual) impairment extends to the domains of language (aphasia),
skilled movements (apraxia), recognition (agnosia), and those functions (such as decision-making and
planning) closely related to the frontal and temporal lobes of the brain as they become disconnected
from the limbic system, reflecting extension of the underlying pathological process. This consists
principally of neuronal loss or atrophy, together with an inflammatory response to the deposition of
amyloid plaques and neurofibrillary tangles. Genetic factors are known to be important, and autosomal
dominant mutations in three different genes (presenilin 1, presenilin 2, and amyloid precursor protein)
have been identified that account for a small number of cases of familial, early-onset AD. For late onset
AD (LOAD), only one susceptibility gene has so far been identified: the epsilon 4 allele of the
apolipoprotein E gene. Age of onset itself has a heritability of around 50%.

Dementia

Dementia (from Latin de- "apart, away" + mens (genitive mentis) "mind") is the progressive
decline in cognitive function due to damage or disease in the brain beyond what might be expected
from normal aging. Particularly affected areas may be memory, attention, language and problem
solving, although particularly in the later stages of the condition, affected persons may be disoriented in
time (not knowing what day, week, month or year it is), place (not knowing where they are) and person
(not knowing who they are). Symptoms of dementia can be classified as either reversible or irreversible
depending upon the etiology of the disease. Less than 10% of all dementias are reversible. Dementia is
a non-specific term that encompasses many disease processes, just as fever is attributable to many
etiologies.

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