417
CHAPTER ELEVEN
Nervous System II
PRACTICE
33
Def
ne
peripheral nervous system.
34
Distinguish between somatic and autonomic nerve f
bers.
35
Distinguish among sensory, motor, and mixed nerves.
36
Describe the structure oF a peripheral nerve.
37
Name the cranial nerves, and list the major Functions oF each.
Spinal Nerves
Thirty-one pairs of spinal nerves originate from the spinal
cord. All but the F
rst pair are mixed nerves, and they pro-
vide two-way communication between the spinal cord and
parts of the upper and lower limbs, neck, and trunk.
The eleventh pair, the
accessory
(ak-ses
o-re)
nerves
(XI, spinal accessory), originate in the medulla oblongata
and the spinal cord; thus, they have both cranial and spinal
branches. Each
cranial branch
of an accessory nerve joins a
vagus nerve and carries impulses to muscles of the soft pal-
ate, pharynx, and larynx. The
spinal branch
descends into
the neck and supplies motor F
bers to the trapezius and ster-
nocleidomastoid muscles. This nerve is considered motor,
with some proprioceptive F
bers.
The twelfth pair, the
hypoglossal
(hi
po-glos
al)
nerves
(XII), arise from the medulla oblongata and pass into the
tongue. They primarily consist of F
bers that carry impulses
to muscles that move the tongue in speaking, chewing, and
swallowing. This nerve is considered motor, with some pro-
prioceptive F bers.
Table 11.9
summarizes the functions of
the cranial nerves.
TABLE
11.9
|
Functions of Cranial Nerves
Nerve
Type
Function
I
OlFactory
Sensory
Sensory f
bers transmit impulses associated with the sense oF smell.
II
Optic
Sensory
Sensory f
bers transmit impulses associated with the sense oF vision.
III
Oculomotor
Primarily motor
Motor f
bers transmit impulses to muscles that raise the eyelids, move the eyes, adjust the amount oF light entering
the eyes, and Focus the lenses.
Some sensory f
bers transmit impulses associated with proprioceptors.
IV
Trochlear
Primarily motor
Motor f
bers transmit impulses to muscles that move the eyes.
Some sensory f
bers transmit impulses associated with proprioceptors.
V
Trigeminal
Mixed
Ophthalmic division
Sensory f
bers transmit impulses From the surFace oF the eyes, tear glands, scalp, Forehead, and upper eyelids.
Maxillary division
Sensory f
bers transmit impulses From the upper teeth, upper gum, upper lip, lining oF the palate, and skin oF the Face.
Mandibular division
Sensory f
bers transmit impulses From the scalp, skin oF the jaw, lower teeth, lower gum, and lower lip.
Motor f
bers transmit impulses to muscles oF mastication and to muscles in the ±
oor oF the mouth.
VI
Abducens
Primarily motor
Motor f
bers transmit impulses to muscles that move the eyes.
Some sensory f
bers transmit impulses associated with proprioceptors.
VII
²acial
Mixed
Sensory f
bers transmit impulses associated with taste receptors oF the anterior tongue.
Motor f
bers transmit impulses to muscles oF Facial expression, tear glands, and salivary glands.
VIII
Vestibulocochlear
Sensory
Vestibular branch
Sensory f
bers transmit impulses associated with the sense oF equilibrium.
Cochlear branch
Sensory f
bers transmit impulses associated with the sense oF hearing.
IX
Glossopharyngeal
Mixed
Sensory f
bers transmit impulses From the pharynx, tonsils, posterior tongue, and carotid arteries.
Motor f
bers transmit impulses to salivary glands and to muscles oF the pharynx used in swallowing.
X
Vagus
Mixed
Somatic motor f
bers transmit impulses to muscles associated with speech and swallowing; autonomic motor f
bers
transmit impulses to the viscera oF the thorax and abdomen.
Sensory f
bers transmit impulses From the pharynx, larynx, esophagus, and viscera oF the thorax and abdomen.
XI
Accessory
Primarily motor
Cranial branch
Motor f
bers transmit impulses to muscles oF the soFt palate, pharynx, and larynx.
Spinal branch
Motor f
bers transmit impulses to muscles oF the neck and back; some proprioceptor input.
XII
Hypoglossal
Primarily motor
Motor f
bers transmit impulses to muscles that move the tongue; some proprioceptor input.
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