In the mechanism of isolation, unpleas-
ant memories (for example, of being
assaulted) are retained but the feelings
that go with them are hidden, so that a
person may recall such an event appar-
ently without emotion.
Administration of one or more brief
electric shocks to the heart, usually via
two metal plates, or paddles, placed on
the chest over the heart. It is performed
to return the heart’s rhythm to normal
in some types of
or rapid heartbeat), such as
Defibrillation can be carried out as
an emergency procedure to treat ven-
tricular fibrillation, w hich is a cause
and most commonly
occurs after a heart attack (see
It can also be used as
a planned treatment, in w hich case it
is performed under a brief general
Breathing may be m ain-
duration of the procedure.
A type of anaemia. See
The removal of excess fluoride from
drinking water, often using domestic
water filters, to prevent
tling of tooth enamel) in consumers.
The toxic effects of plant poisons that
cause leaves to drop off. Defoliants are
poisonous if they are swallowed. Widely
used defoliant poisons include sodium
potassium chlorate, phenoxy
Any malformation or distortion of part
of the body. Deformities may be con-
genital (present from birth), or they
may be acquired as a result of injury,
disorder, or disuse.
Most congenital deformities are rela-
tively rare. Among the more common
cleft lip and
Injuries that can cause deformity
include burns, torn muscles, and bro-
ken bones. Disorders that may cause
deformity include certain nerve prob-
lems, some deficiencies, such as
of the bone. Disuse
of a part of the body can lead to defor-
mity through stiffening and
of unused muscles or tendons.
Many deformities can be corrected
by means of orthopaedic techniques,
or specific exercises.
Physical and/or chemical changes in
organs that reduce
their efficiency. Degeneration is a fea-
ture of aging and may also be due to
disease processes. Other known causes
include injury, reduced blood supply,
poisoning (by alcohol, for example), or
a diet deficient in a specific vitamin.
A term covering a wide range of condi-
in w hich
impairment in the structure and func-
tion of a body system, organ, or tissue.
structures in the organ affected is usu-
ally reduced, and cells are replaced by
or scar tissue. In many
cases, the cause of the disease is poorly
understood, but degenerative disorders
are the subjects of intensive research.
Degenerative nervous system disor-
neuron disease, Huntington’s disease
ders of the eye include Leber’s
disorders of the joints
tion occurs in
Some degree of hardening of the arter-
ies seems to be a feature of normal aging,
changes in the muscle coat of the arteries
are unusually severe, and calcium deposits
may be seen on
(as in Monckeberg’s
sclerosis, a type of
In most cases, there is little that can
be done to slow the progress of the dis-
ease, but it is often possible to relieve
symptoms with drug treatment
example, in Parkinson’s disease).
A rare disorder that affects the linings
of small and medium-sized arteries
throughout the body, particularly in the
intestine, and nervous system,
causing the vessels to become blocked.
The cause is unknown.
The disease typically produces m ulti-
appear as red, raised spots and then
depressed, white scars. Lesions
may then form in arteries supplying
other parts of the body, such as the
intestine and the nervous system. This
development may cause severe or even
life-threatening problems, such as
from lesions that have formed in the
brain and perforation of the intestine by
lesions that penetrate through the intes-
tine wall (see
The splitting open of a partly healed
wound. The term is most commonly
used to refer to the splitting open of a
surgical incision that has been closed
with sutures or clips.
A condition in w hich a person’s
content is at a dangerously low level.
Water accounts for about 60 per cent of
a man’s body weight and about 5
cent of a woman’s. The total content of
water (and mineral salts and other sub-
stances that are dissolved in the body’s
fluids) must be kept within fairly nar-
functioning of cells and tissues.
Dehydration occurs due to inadequate
intake of fluids or excessive fluid loss.
The latter may occur as a result of
severe or prolonged vomiting or diar-
rhoea, or in people who have poorly
and certain types of
Children are particularly susceptible to
dehydration due to diarrhoea.
The symptoms of severe dehydration
are extreme thirst; dry lips and tongue;
an increase in heart rate and breath-
ing rate; dizziness; confusion; lethargy;
The skin looks dry
and loses its elasticity. Any urine passed
is small in quantity and dark-coloured.
If there is also salt depletion (for exam-
ple, due to heavy sweating), there may
be headaches, cramps, and pallor.
Drinking bottled mineral water helps
to maintain the intake of salts. In cases
of persistent vomiting and diarrhoea,
is required; salt and
glucose rehydration mixtures are avail-
able from chemists.
In severe cases of dehydration, fluids
may be given intravenously, and the
water/salt balance is carefully m oni-
tored by means of blood tests and is
adjusted as necessary.