528
UNIT 3
Regulation and Integration of the Body
14
Cranial Part
Preganglionic fibers run in the oculomotor, facial, glossopha-
ryngeal, and vagus cranial nerves. Teir cell bodies lie in associ-
ated motor cranial-nerve nuclei in the brain stem (see Figures
12.13 and 12.14). Next, let’s look at where the neurons of the
cranial parasympathetics are located.
Oculomotor Nerves
Te parasympathetic fibers of the
oculo-
motor nerves (III)
innervate smooth muscles in the eyes that
cause the pupils to constrict and the lenses to bulge—actions
needed to focus on close objects. Te preganglionic axons found
in the oculomotor nerves issue from the
accessory oculomotor
(
Edinger-Westphal
)
nuclei
in the midbrain. Te cell bodies of the
postganglionic neurons are in the
ciliary ganglia
within the eye
orbits (see ±able 13.2, p. 495).
Facial Nerves
Te parasympathetic fibers of the
facial nerves
(VII)
stimulate many large glands in the head.
Fibers that activate the nasal glands and the lacrimal glands
of the eyes originate in the
lacrimal nuclei
of the pons. Te pre-
ganglionic fibers synapse with postganglionic neurons in the
pterygopalatine ganglia
(ter
0
eh-go-pal
9
ah-tīn) just posterior
to the maxillae.
Te preganglionic neurons that stimulate the submandibular
and sublingual salivary glands originate in the
superior saliva-
tory nuclei
of the pons. Tey synapse with postganglionic neu-
rons in the
submandibular ganglia
, deep to the mandibular
angles (see ±able 13.2, p. 497).
Glossopharyngeal Nerves
Te parasympathetics in the
glos-
sopharyngeal nerves (IX)
originate in the
inferior salivatory
nuclei
of the medulla and synapse in the
otic ganglia
, located
just inferior to the foramen ovale of the skull. Te postgangli-
onic fibers course to and activate the parotid salivary glands
anterior to the ears (see ±able 13.2, p. 499).
Cranial nerves III, VII, and IX supply the entire parasympa-
thetic innervation of the head. Note that only the
preganglionic
fibers lie within these three pairs of cranial nerves—
postgangli-
onic
fibers do not. Many of the postganglionic fibers “hitch a
ride” with branches of the
trigeminal nerve
(
V
), taking advan-
tage of its wide distribution.
Vagus Nerves
Between them, the two
vagus nerves (X)
ac-
count for about 90% of all preganglionic parasympathetic fi-
bers in the body. Tey provide fibers to the neck and to nerve
plexuses (interweaving networks of nerves) that serve virtually
every organ in the thoracic and abdominal cavities.
Te vagal nerve fibers (preganglionic axons) arise mostly
from the
dorsal motor nuclei
of the medulla and synapse in ter-
minal ganglia usually located in the walls of the target organ.
Rather than having individual names, most of the terminal gan-
glia are collectively called
intramural ganglia
, literally, “ganglia
within the walls.”
As the vagus nerves pass into the thorax, they send branches
to the
cardiac plexuses
supplying fibers to the heart that slow
heart rate, the
pulmonary plexuses
serving the lungs and bron-
chi, and the
esophageal plexuses
(ĕ-sof
0
ah-je
9
al) supplying the
esophagus.
Eye
Lacrimal
gland
Nasal
mucosa
Ciliary
ganglion
Pterygopalatine
ganglion
Pterygopalatine
ganglion
Submandibular
ganglion
Submandibular
and sublingual
glands
CN III
CN VII
CN IX
CN X
Otic ganglion
Parotid gland
Heart
Lung
Liver and
gallbladder
Stomach
Pancreas
Urinary
bladder
and ureters
Small
intestine
Large
intestine
S
2
Pelvic
splanchnic
nerves
Genitalia (penis, clitoris, and vagina)
Rectum
Celiac
plexus
Inferior
hypogastric
plexus
Cardiac and
pulmonary
plexuses
S
4
Preganglionic
Postganglionic
Cranial nerve
CN
Sacral nerve
S
Figure 14.4
Parasympathetic division of the ANS.
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