SENSATION, ABNORMAL
SEPTICAEMIA
S
environment and about the body's inter-
nal state, to the
central nervous system.
Information is collected by millions of
sense
receptors
found throughout body
tissues and in special sense organs, such
as the
eye.
Certain sensory information,
mainly that from the special sense
organs and skin receptors, enters the
sen-
sory cortex
of the brain, where sensations
are consciously perceived. Other types of
sensory information, for example about
body posture, are processed elsewhere
and do not produce conscious sensation.
sensation, abnormal Dulled, unpleas-
ant, or otherwise altered
sensations
in
the absence of an obvious stimulus.
Numbness
and
pins-and-needles
are
common abnormal sensations. The spe-
cial senses can be impaired by damage
to the relevant sensory apparatus (see
vision, disorders of; smell; deafness; tinni-
tus).
Other causes of abnormal sensation
include peripheral nerve damage caused
by
diabetes mellitus, herpes zoster
infec-
tion, or pressure from a tumour, and
disruption of nerve pathways in the
brain
or
spinal cord
due to
spinal injury, head
injury, stroke,
and
multiple sclerosis.
Pressure on or damage to nerves can
sometimes be relieved by surgery or by
treatments for the cause. In other cases,
distressing abnormal sensation can be
relieved only by cutting the relevant nerve
fibres or by giving injections to block
the transmission of signals.
senses See
sensation.
sensitization The initial exposure of a
person to an allergen or other substance
recognized as foreign by the
immune
system
, which leads to an immune res-
ponse. On subsequent exposures to the
same substance, there is a much stronger
and faster immune reaction. This forms
the basis of allergy and other types of
hypersensitivity
reaction.
sensorineural deafness
Deafness
due
to problems with the inner ear, nerves,
or the brain's auditory area.
sensory cortex A region of the outer
cerebrum
of the
brain
in which sensory
information comes to consciousness.
Pressure, pain, and temperature sen-
sations from the skin, muscles, joints,
and organs are perceived in the parietal
lobes, as is taste. Visual sensations are
perceived in the occipital lobes at the
back of the cerebrum; sound is perceived
in the temporal lobes at the sides.
sensory deprivation The removal of
normal external stimuli, such as sight
and sound, from a person's environment.
Prolonged sensory deprivation can pro-
duce feelings of unreality, difficulty in
thinking, and
hallucinations.
separation
anxiety The feelings of
distress a young child experiences when
parted from his or her parents or home.
This is a normal aspect of infant behav-
iour and usually diminishes by age 3 or 4.
In separation anxiety disorder, the
reaction to separation is greater than
that expected for the child's level of de-
velopment. The anxiety may manifest as
physical symptoms. Separation anxiety
disorder may be a feature of
depression.
sepsis Infection of a wound or body tis-
sues with bacteria that leads to the
formation of
pus
or to the multiplication
of the bacteria in the blood. (See also
bacteraemia; septicaemia; septic shock.
)
septal defect A congenital
heart
abnor-
mality in which there is a hole in the
septum between the left and right ven-
tricles of the heart or, more rarely,
between the left and right atria. Usually,
the cause is unknown. The hole allows
freshly oxygenated blood to mix with
deoxygenated blood in the heart.
A small defect has little or no effect. A
large ventricular hole may cause
heart
failure
to develop
6 -8
weeks after birth,
causing breathlessness and feeding dif-
ficulties. A large atrial defect may never
cause heart failure, but there may be
fatigue on exertion.
Pulmonary hyperten-
sion
may develop in both types of defect.
Diagnosis may be aided by a
chest
X-ray
,
ECG
, or
echocardiography
.
Atrial holes are repaired surgically if
they cause symptoms or if complications
develop. As the child grows, small ven-
tricular holes often become smaller, or
even close, on their own. A ventricular
defect that is causing heart failure is
treated with
diuretics
and
digtalis drugs.
If the hole does not close spontaneously,
it may be repaired by
open heart surgery
.
septicaemia A potentially life-threaten-
ing condition in which there is rapid
multiplication of bacteria and in which
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