Cranial nerves

CRANIAL
NERVES

By
Sriloy Mohanty
B.N.Y.S
S-VYASA

INTRODUCTION
 There are 12 pairs of cranial nerves in our body
 These are called as cranial nerve because the
originated directly from the brain; inside the cranium
 There names are
 Olfactory nerve oVestibulocochlear nerve
oGlossopharangial nerve
 Optic nerve
oVagus nerve
 Oculomotor nerve oAccessory nerve
 Trochlear nerve oHypoglossal nerve
 Trigeminal nerve
 Abducens nerve
 Facial nerve

SUMMARY OF FUNCTION
OF CRANIAL NERVES

CRANIAL NERVE I:
OLFACTORY
 Arises from the olfactory epithelium
 Passes through the cribriform plate of the
ethmoid bone
 Fibers run through the olfactory bulb and
terminate in the primary olfactory cortex
 Functions solely by carrying afferent impulses for
the sense of smell

CRANIAL NERVE II: OPTIC
 Arises from the retina of the eye
 Optic nerves pass through the optic canals
and converge at the optic chiasm
 They continue to the thalamus where they
synapse
 From there, the optic radiation fibers run
to the visual cortex
 Functions solely by carrying afferent
impulses for vision

CRANIAL NERVE III:
OCULOMOTOR
 Fibers extend from the ventral midbrain,
pass through the superior orbital fissure,
and go to the extrinsic eye muscles
 Functions in raising the eyelid, directing
the eyeball, constricting the iris, and
controlling lens shape
 The latter 2 functions are
parasympathetically controlled
 Parasympathetic cell bodies are in the
ciliary ganglia

CRANIAL NERVE III:
OCULOMOTOR

CRANIAL NERVE IV:
TROCHLEAR

 Fibers emerge from the dorsal midbrain and
enter the orbits via the superior orbital fissures;
innervate the superior oblique muscle
 Primarily a motor nerve that directs the eyeball

CRANIAL NERVE IV:
TROCHLEAR

CRANIAL NERVE V:
TRIGEMINAL
 Composed of three divisions
 Ophthalmic (V1)
 Maxillary (V2)
 Mandibular (V3)
 Fibers run from the face to the pons via the superior
orbital fissure (V1), the foramen rotundum (V2), and the
foramen ovale (V3)
 Conveys sensory impulses from various areas of the face
(V1) and (V2), and supplies motor fibers (V3) for mastication
 Tic douloureux or trigeminal neuralgia
- Most excruciating pain known (?)
- Caused by inflammation of nerve
- In severe cases, nerve is cut; relieves agony but results in loss
of sensation on that side of the face

CRANIAL NERVE VI:
ABDUCENS
 Fibers leave the inferior pons and enter the orbit via the
superior orbital fissure
 Primarily a motor nerve innervating the lateral rectus
muscle (abducts the eye; thus the name abducens)

CRANIAL NERVE VII:
FACIAL
 Fibers leave the pons, travel through the internal
acoustic meatus, and emerge through the stylomastoid
foramen to the lateral aspect of the face
 Motor functions include;
 Facial expression
 Transmittal of parasympathetic impulses to lacrimal
and salivary glands (submandibular and sublingual
glands)
 Sensory function is taste from taste buds of anterior
two-thirds of the tongue

CRANIAL NERVE VII:
FACIAL

FACIAL NERVE (CN VII)
 Bell’s palsy: paralysis of facial muscles on affected side and
 loss of taste sensation
 Caused by herpes simplex I virus
 Lower eyelid droops
 Corner of mouth sags
 Tears drip continuously and eye cannot be completely closed
 (dry eye may occur)
 Condition my disappear spontaneously without treatment

CRANIAL NERVE VIII:
VESTIBULOCOCHLEAR
 Fibers arise from the hearing and
equilibrium apparatus of the inner ear,
pass through the internal acoustic
meatus, and enter the brainstem at the
pons-medulla border
 Two divisions – cochlear (hearing) and
vestibular (balance)
 Functions are solely sensory – equilibrium
and hearing

CRANIAL NERVE VIII:
VESTIBULOCOCHLEAR

CRANIAL NERVE IX:
GLOSSOPHARYNGEAL
 Fibers emerge from the medulla, leave the
skull via the jugular foramen, and run to
the throat
 Nerve IX is a mixed nerve with motor and
sensory functions
 Motor – innervates part of the tongue and
pharynx, and provides motor fibers to the
parotid salivary gland
 Sensory – fibers conduct taste and general
sensory impulses from the tongue and
pharynx

CRANIAL NERVE IX:
GLOSSOPHARYNGEAL

CRANIAL NERVE X: VAGUS
 The only cranial nerve that extends beyond the
head and neck
 Fibers emerge from the medulla via the
jugular foramen
 The vagus is a mixed nerve
 Most motor fibers are parasympathetic fibers
to the heart, lungs, and visceral organs
 Its sensory function is in taste
 Paralysis leads to hoarseness
 Total destruction incompatible with life

CRANIAL NERVE XI:
ACCESSORY
 Formed from a cranial root emerging from
the medulla and a spinal root arising from
the superior region of the spinal cord
 The spinal root passes upward into the
cranium via the foramen magnum
 The accessory nerve leaves the cranium via
the jugular foramen
 Primarily a motor nerve
 Supplies fibers to the larynx, pharynx, and soft
palate
 Innervates the trapezius and
sternocleidomastoid, which move the head and
neck

CRANIAL NERVE XI:
ACCESSORY

CRANIAL NERVE XII:
HYPOGLOSSAL

 Fibers arise from the medulla and exit the skull via
the hypoglossal canal
 Innervates both extrinsic and intrinsic muscles of
the tongue, which contribute to swallowing and
speech
 If damaged, difficulties in speech and
swallowing; inability to protrude tongue

CRANIAL NERVE XII:
HYPOGLOSSAL

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