Bma Illustrated Medical Dictionary

nerve injuryDamage or severance of
conducting fibres within a nerveas a
result of trauma, causing loss of skin
sensation and muscle power. (See neuro-
pathyfor nerve damage from causes
other than injury.)
If a peripheral nerve (a nerve outside
the brain or spinal cord) is only partially
severed, the cut fibres may be able to
regenerate. Provided the severed ends
are still aligned, new fibres can grow
across the cut to rejoin the connection,
restoring function. If a nerve is totally
severed, the individual fibres cannot
regenerate successfully and there is no
recovery of function. Nerve tracts within
the brain and spinal cord are structural-
ly different from the peripheral nerves,
and severed fibres in these tracts do not
regenerate. For example, vision cannot
be restored if the optic nervesare cut.
Microsurgerycan sometimes be used
to stitch a severed peripheral nerve into
place, but recovery is rarely complete.
nerve, trappedCompression or stretch-
ing of a nerve, causing numbness,
tingling, weakness, and, sometimes, pain.
Common examples of a trapped nerve
include carpal tunnel syndrome, in which
pressure on the median nerve as it
passes through the wrist causes symp-
toms in the thumb, index, and middle
fingers; a disc prolapse, in which pressure
on the nerve root leading from the spinal
cord produces symptoms in the back
and legs; and crutch palsy, in which the
radial nerve presses against the humerus
(upper-arm bone), producing symptoms
in the wrist and hand.
A damaged nerve may take some time
to heal. In severe cases, surgical decom-
pression to relieve pressure on the nerve
may be necessary.
nervous breakdownA nontechnical
term used to describe unusual behav-
iour (such as episodes of tearfulness or
shouting and screaming) that may be
part of a crisis of severe anxiety, depres-
sion, or other psychiatric illness. The
condition affects the sufferer’s ability to
cope with everyday life.
nervous energyA nontechnical term
for the increased drive and activity of
individuals who are always restless,
anxious, and on the go.

nervous habitA nontechnical term for

a minor repetitive movement or activity.

Sometimes a nervous habit consists of

involuntary twitches and facial tics,

such as in Gilles de la Tourette’s syn-

dromeand some forms of dyskinesia.

Voluntary nervous habits, such as nail-

bitingand thumb-sucking, are common

in young children.

All nervous habits increase during

periods of tension or anxiety, and may

be severe in some forms of depression,

anxiety disorder, or drug withdrawal.

nervous systemThe body system that

gathers and stores information and is in

overall control of the body.

NERVE INJURY NERVOUS SYSTEM

N

Optic nerve

Facial nerve

Cerebellum

Spinal cord

Femoral

nerve

Tibial

nerve

Dorsal

digital

nerves

Medial dorsal

cutaneous

nerve

Superficial

peroneal

nerve

Deep

peroneal

nerve

Common

peroneal

nerve

Sciatic

nerve

Median

nerve

Ulnar

nerve

Radial

nerve

Spinal

nerve

Cerebrum

of brain

Vagus nerve

Skull

NERVOUS SYSTEM