CEREBROVASCULAR DISEASE
C
obstruction to blood circulation, and
leads to a
stroke
(damage to part of the
brain due to interrupted blood supply).
Blockage may be due to
thrombosis
(clot formation) or to
embolism
(a clot
fragment, or an air bubble carried in
the circulation). Rupture of vessels may
result in different patterns of bleeding:
intracerebral haemorrhage
(bleeding in
the brain) or
subarachnoid haemorrhage
(bleeding around the brain).
cerebrovascular disease
Any disease affecting an artery supply-
ing blood to areas inside the brain.
Such
diseases
include
atherosclerosis
(narrowing of the arteries) and defects
in arterial walls that cause
aneurysm
(a
balloon-like swelling in an artery).
The disease may eventually cause a
cerebrovascular accident
,
w hich
com-
monly results
in a
stroke
.
Extensive
narrowing of blood vessels throughout
the brain can be a cause of
dementia
.
cerebrum
The largest and most developed part of
the
brain
,
and the site of most con-
scious and intelligent activities.
STRUCTURE
The main components of the cerebrum
are two large hemispheres that grow
out from the upper part of the
brain-
stem
(an extension of the spinal cord).
The surface of the cerebrum is made up
of a series of folds called gyri, w hich
are separated by fissures called sulci,
w ith a deep longitudinal fissure sepa-
rating the two hemispheres.
The four main surface regions of
each hemisphere - the frontal, pari-
etal, temporal, and occipital lobes - are
named after the bones that are over-
lying them. Each hemisphere has a
central cavity, called a
ventricle
,
that is
filled w ith
cerebrospinal fluid
.
This cavi-
ty is surrounded by an inner layer,
consisting of clusters of nerve cells
called the
basal ganglia
.
There is a m id-
dle
layer
of
white matter
composed
mainly of nerve fibres, w hich carry
information between particular areas
of the
cortex
and between the cortex,
central brain, and
brainstem
.
The outer
surface layer of each hemisphere is the
cerebral cortex, w hich is also known as
the
grey matter
,
where much of the sen-
sory information from organs such as
the eyes and the ears is processed. A
thick band of fibres called the corpus
callosum carries nerve signals between
the two cerebral hemispheres.
FUNCTION
Specific sensory processing takes place
in separate regions. For example, visual
perception is located in a part of the
occipital lobe called the visual cortex.
The cortex also contains “motor’’
areas concerned w ith initiating signals
for movements of the skeletal muscles.
Linked to the sensory and motor areas
of the
cortex
are
association
areas.
These
regions
integrate
information
from various senses and also perform
functions such as comprehension and
recognition, memory storage and re-
call, thought, and decision-making.
Some cortical functions are localized
to one “ dominant’’ hemisphere
(the
left in
almost all
right-handed and
many left-handed people). Two clearly
defined areas in the dominant hem i-
sphere are Wernicke’s area, w hich is
responsible for the comprehension of
spoken
and
written
language,
and
Broca’s area, w hich is concerned with
language expression.
DISORDERS
Damage to particular areas of the cere-
brum may cause specific syndromes.
For example,
damage to the frontal
lobe may cause mental apathy, whereas
a parietal lobe injury may result in geo-
graphical disorientation. Disease of the
temporal
lobe
may
cause
amnesia
(memory loss), and visual defects may
result from occipital lobe damage.
Quite often, however, cerebral dis-
ease causes nonspecific symptoms such
as convulsions and headaches.
certification
An outdated term for procedures to
commit a person to be compulsorily
detained for mental health treatment.
cerumen
The medical term for
earwax
.
Cerumol
A brand-named preparation used for
the removal of
earwax.
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