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CHAPTER ELEVEN
Nervous System II
A disorder of the trigeminal nerve called
trigeminal neuralgia
(tic dou-
loureux) causes severe recurring pain in the face and forehead on the
aF
ected side. If drugs cannot control the pain, surgery may be used
to sever the sensory part of the nerve. However, the patient loses
sensations in other body regions that the sensory branch supplies.
Consequently, after such surgery, care must be taken when eating or
drinking hot foods or liquids, and the mouth must be inspected daily
for food particles or damage to the cheeks from biting.
The sixth pair, the
abducens
(ab-du
senz)
nerves
(VI),
are small and originate from the pons near the medulla
oblongata. They enter the orbits of the eyes and supply motor
impulses to the remaining pair of external eye muscles, the
lateral rectus muscles.
This nerve is considered motor, with
some proprioceptive F
bers.
The seventh pair of cranial nerves, the
facial
(fa
shal)
nerves
(VII), are mixed nerves that arise from the lower
part of the pons and emerge on the sides of the face. Their
sensory branches are associated with taste receptors on the
anterior two-thirds of the tongue, and some of their motor
fibers transmit impulses to muscles of facial expression
(f
g. 11.27)
. Still other motor F bers of these nerves function
in the autonomic nervous system by stimulating secretions
from tear glands and certain salivary glands (submandibular
and sublingual glands).
The fourth pair, the
trochlear
(trok
le-ar)
nerves
(IV),
are the smallest cranial nerves. They arise from the midbrain
and carry motor impulses to a F
fth pair of external eye mus-
cles, the
superior oblique muscles,
which are not supplied by
the oculomotor nerves. This nerve is considered motor, with
some proprioceptive F
bers.
The F
fth pair, the
trigeminal
(tri-jem
i-nal) nerves (V),
are the largest of the cranial nerves and arise from the pons.
They are mixed nerves, with the sensory portions more
extensive than the motor portions. Each sensory component
includes three large branches, called the ophthalmic, maxil-
lary, and mandibular divisions
(f
g. 11.26)
.
The
ophthalmic division
consists of sensory F bers that
bring impulses to the brain from the surface of the eye; the
tear gland; and the skin of the anterior scalp, forehead, and
upper eyelid. The F
bers of the
maxillary division
carry sen-
sory impulses from the upper teeth, upper gum, and upper
lip, as well as from the mucous lining of the palate and facial
skin. The
mandibular division
includes both motor and sen-
sory F bers. The sensory branches transmit impulses from the
scalp behind the ears, the skin of the jaw, the lower teeth,
the lower gum, and the lower lip. The motor branches sup-
ply the muscles of mastication and certain muscles in the
fl oor of the mouth.
Lacrimal nerve
Ophthalmic
division
Maxillary
division
Mandibular
division
Lingual
nerve
Inferior
alveolar
nerve
Lacrimal
gland
Eye
Infraorbital
nerve
Maxilla
Tongue
Mental
nerve
Mandible
FIGURE 11.26
Each trigeminal nerve has three large branches that
supply various regions of the head and face: the ophthalmic division
(sensory), the maxillary division (sensory), and the mandibular division
(sensory and motor to muscles of mastication).
Temporal nerve
Zygomatic nerve
Buccal nerve
Facial nerve
Posterior auricular
nerve
Parotid salivary
gland
Mandibular nerve
Cervical nerve
FIGURE 11.27
The facial nerves are associated with taste receptors
on the tongue and with muscles of facial expression.
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