I M
The Peripheral Nervous System
Communicates with the Outside World
LEARNING OBJECTIVES
1.
Describe
the parts of a nerve.
2.
Identify
the 12 pairs of cranial nerves and the
type of information carried by each.
T
he
CNS
communicates with
the
outside
world through the peripheral nervous sys-
tem (PNS), which consists of cranial nerves
and peripheral, or spinal, nerves. Nerves are
3.
Outline
the distribution of spinal nerves.
4.
Explain
how a reflex arc works.
collections of neuronal axons wrapped into bundles by
various connective tissue coverings. These bundles are in
turn wrapped together again, much like wires in a con-
duit (Figure 7.17). Most nerves carry both sensory and
T
P arts o f a n erv e • Figure 7.17
EPINEURIUM around
entire nerve
Fascicle
PERINEURIUM
around each
fascicle
Myelin
sheath
Blood vessels
ENDONEURIUM around
Axon
each axon
Transverse section showing the parts and coverings of a nerve
Cranial n erves • Figure 7.18
The cranial nerves provide sensory and motor functions for the
head, special senses (sight, hearing, smell, taste), and parasym-
pathetic outputs to the body.
NERVE
FUNCTION
I
Sensory for smell
II
Sensory for vision
III
Motor for eye movement
and focusing
IV
Motor for eye movement
V
Sensory from face
and motor for chewing
VI
Motor for eye movement
VII
Sensory for taste and motor
for facial movement
VIII
Sensory for hearing
and equilibrium
IX
Sensory for taste and blood
pressure and motor for
swallowing and speech
X
Sensory and motor associated
with thoracic and
abdominal organs
XI
Motor to muscles of head,
neck, and shoulders
XII
Motor to tongue
Mnemonic
for
remembering the names of the
cranial
nerves
Oh, Oh, Oh, To Touch And Feel Very Green Vegetables AH!
214 CHAPTER 7
The Nervous System
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