Enhanced From Wikipedia, the Free
Encyclopedia
Cranial nerves are
nerves that emerge directly from the
brain in contrast to
spinal nerves which emerge from segments of the
spinal cord. Although thirteen cranial nerves in
humans fit this description, twelve are conventionally
recognized. The nerves from the third onward arise from the
brain stem. Except for the tenth and the eleventh nerve,
they primarily serve the
motor and
sensory systems of the
head and neck region. However, unlike
peripheral nerves which are separated to achieve
segmental innervation, cranial nerves are divided to
serve one or a few specific functions in wider anatomical
territories.
Names
of Nerves
The 12 pairs of cranial nerves are traditionally
abbreviated by the corresponding
Roman numerals. They are numbered according to where
their
nuclei lie in the brain stem, e.g. Cranial Nerve III
(the Oculomotor nerve) leaves the brainstem at a higher
position than Cranial nerve XII, whose origin is located
more caudally (lower) than the other cranial nerves.
|
# |
Name |
Function |
Tam Reference |
|
0 |
Cranial nerve zero (CN0 is not traditionally
recognized.)
|
Still controversial. New research indicates CN0
may play a role in the detection of pheromones
|
(C3) |
|
I |
Olfactory nerve
|
Transmits the sense of smell; Located in
olfactory foramina of ethmoid |
(C3) |
|
II |
Optic nerve |
Transmits visual information to the brain;
Located in
optic canal |
(GB19, c3) |
|
III |
Oculomotor nerve
|
Innervates
levator palpebrae superioris,
superior rectus,
medial rectus,
inferior rectus, and
inferior oblique, which collectively perform
most eye movements; Located in
superior orbital fissure |
(Motor Cortex GV21,
temples) |
|
IV |
Trochlear nerve |
Innervates the
superior oblique muscle, which depresses, pulls
laterally, and
intorts the eyeball; Located in
superior orbital fissure |
(C3,
Motor Cortex GV21, eye) |
|
V |
Trigeminal nerve |
Receives sensation from the face and innervates
the
muscles of mastication; Located in
superior orbital fissure (ophthalmic branch),
foramen rotundum (maxillary branch), and
foramen ovale (mandibular branch) |
(C3,C4, jaw) |
|
VI |
Abducens nerve |
Innervates the
lateral rectus, which abducts the eye; Located
in
superior orbital fissure |
(C3,
Motor Cortex GV21, eye) |
|
VII |
Facial nerve |
Provides motor innervation to the
muscles of facial expression and
stapedius, receives the special sense of taste
from the
anterior 2/3 of the tongue, and provides
secretomotor innervation to the
salivary glands (except parotid) and the
lacrimal gland; Located and runs through
internal acoustic canal to
facial canal and exits at
stylomastoid foramen |
(Sky
Window. C3,C4, facial artery) |
|
VIII |
Vestibulocochlear nerve (or
auditory-vestibular nerve or statoacustic
nerve) |
Senses sound, rotation and gravity (essential
for balance & movement; Located in
internal acoustic canal |
(C3,C4,
ear) |
|
IX |
Glossopharyngeal nerve |
Receives taste from the posterior 1/3 of the
tongue, provides secretomotor innervation to the
parotid gland, and provides motor innervation to the
stylopharyngeus (essential for tactile, pain,
and thermal sensation). Sensation is relayed to
opposite thalamus and some hypothalamic nuclei.
Located in
jugular foramen |
(C4,C5) |
|
X |
Vagus nerve |
Supplies branchiomotor innervation to most
laryngeal and pharyngeal muscles; provides
parasympathetic fibers to nearly all thoracic
and abdominal viscera down to the
splenic flexure; and receives the special sense
of taste from the epiglottis. A major function:
controls muscles for voice and resonance and the
soft pallet. Symptoms of damage:
dysphagia (swallowing problems). Located in
jugular foramen |
(ST12,
KD27-KD11) |
|
XI |
Accessory nerve (or cranial accessory nerve
or spinal accessory nerve) |
Controls muscles of the neck and overlaps with
functions of the vagus. Examples of symptoms of
damage: inability to shrug, weak head movement,
velopharyngeal insufficiency; Located in
jugular foramen |
(TianDong or vertebral artery,
sky window) |
|
XII |
Hypoglossal nerve |
Provides motor innervation to the muscles of the
tongue and other glossal muscles. Important for
swallowing (bolus formation) and speech
articulation. Located in
hypoglossal canal |
(C4,C5) |
Cranial
nerves in non-human vertebrates
Human cranial nerves are
evolutionarily
homologous to those found in many other
vertebrates. Cranial nerves XI and XII evolved in the
common ancestor to
amniotes (non-amphibian tetrapods) thus totalling twelve
pairs. These characters are
synapomorphies for their respective
clades. In some primitive cartilagenous fishes, such as
the
dogfish (Squalos acanthos), there is a terminal
nerve numbered
zero (as it exits the brain before the first cranial
nerve).
