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THE CRANIAL NERVES
HONORS
ANATOMY & PHYSIOLOGY
CRANIAL NERVES
 12-pair
 named “cranial” because each passes thru a
foramina of the cranium
 part of PNS
 each with roman numeral (order from anterior 
posterior in which nerves arise from base of brain) &
a name that indicates nerve distribution
CRANIAL NERVES
 classified as:
sensory
2. motor
3. mixed (sensory & motor)
1.
Cranial Nerve I: Olfactory
 olfact = to smell
 sensory
 olfactory epithelium on superior surface of nasal
cavity just inferior to cribiform plate of ethmoid bone
 olfactory receptors are bipolar neurons
each: single odor-sensitive dendrite
 their unmyelinated axons join above plate form
rt or lt olfactory nerves

Course of Olfactory Nerve
 olfactory nerves end in pair of olfactory bulbs:
masses of gray matter resting just above cribiform
plate where they synapse with next neurons in
olfactory pathway
Course of Olfactory Nerve
 axons of these neurons make up the olfactory tracts
 posteriorly to primary olfaction center in temporal
lobe
Cranial Nerve II: Optic Nerve
 optic = eye
 sensory
 rods & cones in retina: receptors initiating visual
signals & relay them  bipolar cells  optic
ganglion neurons  their axons join forming optic
nerves
 pass thru optic foramen  optic chiasm: a cross-over
of medial half of each eye to opposite side (lateral
half does not cross
Optic Chiasm
Optic Tracts
 from optic chiasm  optic tracts
most axons  thalamus  synapse with neurons
whose axons  primary visual area of occipital
lobe
 some axons synapse with motor neurons in
midbrain extrinsic eye muscles

Cranial Nerve III: Oculomotor
 oculo = eye
 mixed, mainly motor
 its motor nucleus in
ventral part of midbrain
 2 branches pass thru
superior orbital fissure
Oculomotor Nerve Extrinsic Muscles of Eye
Inferior Branch
Superior Branch
 axons innervate:
 axons innervate:
superior rectus
2. levator palpebrae
superioris (upper
eyelid)
1.
1.
medial rectus
2. inferior rectus
3. inferior oblique
Oculomotor Nerve
 inferior branch also:

1.
2.
parasympathetic innervation to intrisic muscle of
eye (smooth muscle)
ciliary muscle: adjusts lens for near/far vision
circular muscle of iris: contracts/relaxes in
response to amt of light (pupils constrict/dilate)
Oculomotor Nerve: Sensory
 proprioception: nonvisual perception of movements
& positions of body
Cranial Nerve IV: Troclear Nerve
 trochle = pulley
 mixed, mainly motor
 smallest of the 12 cranial nerves
 only 1 that arises from posterior of midbrain
Cranial Nerve IV: Troclear Nerve
 motor:
 axons from nucleus in midbrain  superior orbital
fissure
 innervates superior oblique muscle
 sensory: proprioception in superior oblique
Cranial Nerve IV: Troclear Nerve
Trigeminal Nerve V
 largest of 12 cranial nerves
 mixed:
sensory: ganglion in temporal bone
 motor: neurons in pons

Cranial Nerve V: Trigeminal Nerve
 tri: has 3 branches
Ophthalmic: sensory only: upper eyelids, eyes,
lacrimal glands, upper nasal cavity, side of nose,
forehead, anterior ½ of scalp
2. Maxillary: sensory only: mucosa of nose, palate,
part of pharynx, upper teeth, upper lip, lower
eyelids
3. Mandibular: sensory: anterior 2/3 of tongue (not
taste), cheek, lower teeth
motor: muscles of mastication
1.
Trigeminal Nerve
Cranial Nerve VI: Abducens Nerve
 ab: away / ducens: to lead (nerve impulses causes
abduction of eyeball)
 mixed mainly motor
 nucleus in pons (motor): innervates lateral rectus
muscle
 sensory: proprioception in lateral rectus
Abducens Nerve
On Which Side is VI not Functioning?
Cranial Nerve VII: Facial Nerve
 mixed
 sensory:
 taste buds anterior 2/3 of tongue, proprioceptors
in face & scalp
 motor:
 nucleus in pons
 innervates muscles of facial expression +
stylohyoid muscle & posterior belly of digastric
muscle
 parasympathetic: lacrimal glands, palatine glands,
salivary glands: sublingual & sub-mandibular
Facial Nerve
Cranial Nerve VIII: Vestibulocochlear Nerve
 vestibule:small cavity; cochlear: snail-like
 mixed, mainly sensory
 2 branches
Vestibular:
1.

equilibrium
2. Cochlear:


hearing
motor: hair cells of spiral organ
Cranial Nerve IX: Glossopharyngeal Nerve
 glosso:tongue, pharyngeal: throat
 Mixed
 sensory: taste buds & somatic sensory receptors on
posterior 1/3 tongue, proprioceptors in swallowing
muscles, baroreceptors (stretch) in carotid sinus,
chemoreceptors in carotid bodies
 motor: from nuclei in medulla, exit thru jugular
foramen, innervate stylopharyngeus muscle (elevates
pharynx & larynx)
 parasympathetic: motor: stimulate parotid gland to
secrete saliva
Cranial Nerve X: Vagus Nerve
 vagus: wanderer, vagrant
 mixed
 distributed from head  abdomen
Vagus Nerve
 sensory:
skin of external ear
 taste buds in epiglottis & pharynx
 proprioceptors in muscles of neck & throat
 baroreceptors in arch of aorta & chemoreceptors
in aortic bodies
 visceral sensory receptors in most organs of
thorax & abdominal cavities

Vagus Nerve
 parasympathetic motor:
heart & lungs
 glands in GI tract
 smooth muscle of airways, esophagus, stomach,
gall bladder, small intestine, most of large
intestine

Distribution of Vagus Nerve
Cranial Nerve XI: Accessory Nerve
 mixed
 originates from both the brainstem & spinal cord
 cranial root:
motor: from medulla thru jugular foramen
 supplies voluntary muscles of pharynx, larynx, &
soft palate

 spinal root:
mixed, mainly motor
 motor:

Cranial Nerve XI: Accessory Nerve
 spinal root:
mixed, mainly motor
 motor: neurons in anterior gray horn of C1 – C5
 axons come together  foramen magnum 
jugular foramen
 innervates sternocleidomastoid & trapezius
muscles
 sensory: proprioceptors in muscles it supplies

Cranial Nerve XII: Hypoglossal
 hypo: below, glossal: tongue
 mixed
 sensory:proprioceptors in tongue muscles 
medulla
 motor: nucleus in medulla  hypoglossal canal 
muscles of the tongue (speech, swallowing)
Development of the Nervous System
 begins developing in 3rd
wk from a thickening of
ectoderm called the
neural plate
Development of the Brain & Spinal Cord