motor neurons (mixed); however, some cranial nerves
carry sensory neurons only (sensory nerves) or motor
neurons only (motor nerves). Let’s start by looking at
cranial nerves.
Cranial Nerves Originate
from Brain Tissue
There are 12 pairs of cranial nerves. Each pair of nerves
is numbered with a Roman numeral that designates the
order in which it emerges from the brainstem. Cranial
nerves I, II, and VIII are sensory nerves, and cranial nerves
III, IV, VI, XI, and XII are motor nerves; see Figure 7.18
for the specific functions of each pair. The cell bodies of
sensory neurons in the cranial nerves lie in ganglia out-
side the brain, while those of motor neurons are located in
nuclei within the brain. The major functions of the cranial
nerves are sensory and motor functions of the face and
head, special senses, and ANS output (Figure 7.18).
Now let’s examine spinal nerves.
ANTERIOR
CRANIAL NERVES:
Olfactory (I) nerve
Optic (II) nerve
Oculomotor (III) nerve
Trochlear (IV) nerve
Trigeminal (V) nerve
Abducens (VI) nerve
Facial (VII) nerve
Vestibulocochlear (
VIII
)
nerve
Glossopharyngeal (IX)
nerve
Vagus (X) nerve
Accessory (XI) nerve
Hypoglossal (XII) nerve
Cerebrum
Olfactory bulb
Olfactory tract
Optic tract
Pons
Medulla
oblongata
Spinal nerve C1
Spinal cord
Cerebellum
POSTERIOR
Inferior aspect of brain
The Peripheral Nervous System Communicates with the Outside World
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