CRANIAL NERVES
Cranial Nerves
INTRO TO NEURO
MBCHB
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Overview of Cranial Nerves
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Attached directly to the brain
The cranial nerves contain both afferent and efferent axons that belong to
either the somatic or autonomic nervous system.
Cranial nerve fibres originate and terminate at specific nuclei, which are
similarly classified as either special, somatic, or visceral, and afferent or
efferent.
Nomenclature: based on several factors
•Appearance: Vagus(wanderer)
•Region of innervation (Facial or Hypoglossal)
•Function (sensory or motor)
•Direction of conduction (‘afferent’ –towards CNS and ‘efferent’ –away from CNS)
•Types of tissue innervated (somatic or visceral)
Cranial Nerves in Humans
12 bilaterally paired nerves attached to the brain
Named and numbered as follows
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Cerebrum: Olfactory (I); Optic (II)
Midbrain: Oculomotor (III); Trochlear (IV)
Pons: Trigeminal (V); Abducent (VI); Facial (VII); Vestibulocochlear (VIII)
Medulla: Glossopharyngeal (IX); Vagus (X); Accessory (XI); Hypoglossal (XII)
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Olfactory Nerve (I)
Origin:
- Neurons from mucosa of upper part of nasal cavity
- Pass via cribriform foramina
End:
- Olfactory Bulb (largest neuron called mitral cell)
Course:
- Olfactory mucosa to olfactory cortex in forebrain
- Olfactory tracts from bulb divide into lateral and medial striae
 Lateral stria- lateral olfactory area of cerebral cortex and amygdala
 Medial stria- opposite olfactory bulb via anterior commissure
Component fibre
- Sensory
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Optic Nerve (II)
Origin:
- Ganglionic cells of retina
Course:
- Exits as optic nerve
- Pass through optic canal
- Unites with that of opposite side to form optic chiasma
- Continues as optic tract and e d in Lateral Geniculate Body (LGB) and by
extension superior colliculus and primary visual cortex
Component Fibre:
- Sensory
Function:
- Vision
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Oculomotor Nerve (III)
Origin:
- Oculomotor nucleus (motor)
- Edinger- Westphal nucleus (Parasympathetic)
Course:
- Lies on medial side of cerebral peduncles, in close relation with tentorium
cerebelli
- Branches into superior and inferior and these enter orbit through superior
orbital fissure.
Component fibre:
- Motor and parasympathetic
Function:
- Moves extraocular muscles
- Superior, inferior, medial recti, inferior oblique, levator palpebral superioris
- Sphincter pupillae muscle of iris and ciliary muscle constricts pupil and
accommodates lens
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Trochlear Nerve (IV)
Origin:
- Trochlear nucleus in midbrain
- Most slender and longest of cranial nerves
Course:
- Only nerve to emerge from dorsal part of brainstem
- Passes onto lateral wall of cavernous sinus, crosses CN III and enters orbit
through superior orbital fissure, above common tendinous ring of recti
muscles.
- The only cranial nerve in which all the nerve fibres cross to the opposite side.
- Longest intradural course of any cranial nerve
Component fibre:
- Motor
Function:
- Motor to superior oblique extraocular muscle
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Abducens Nerve (VI)
Origin:
- Abducens nucleus
Course:
- Emerges between pons and medulla
- Longest course in subarachnoid space
- Enters orbit through superior orbit fissure
Component fibres:
- Motor
Functions:
- Supplies lateral rectus extraocular muscle
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Cranial Nerves of the Extraocular Muscles
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Trigeminal Nerve (V)
Largest Cranial Nerve
Origin:
- Trigeminal Sensory Nucleus
 Mesencephalic nucleus
 Pontine (chief) nucleus
 Spinal nucleus
- Trigeminal Motor Nucleus
- Forms the trigeminal ganglion
Course:
- Has 3 division
- Ophthalmic- passes through superior orbital fissure
- Maxillary- passes through foramen rotundum
- Mandibular- passes through foramen ovale
Component fibre:
- Sensory
- Motor (parasympathetic fibres from Cn VII hitchhike with branches of CN V)
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CN V- Branches
Ophthalmic Nerve (V1)
Sensory:
- Scalp, eye, upper face, sinuses
Carries:
- Parasympathetic via ciliary ganglion to eye for accommodation and pupil
constriction (short ciliary nerves), also via pterygopalatine ganglion for lacrimal
gland
- Sympathetic via cavernous sinus to pupil for dilation (long ciliary nerves)
Main branches:
- Frontal
- Lacrimal
- Nasociliary
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Maxillary Nerve (V2)
Sensory:
- Middle face, palate, sinuses, nasopharynx, nose
Carries:
- Parasympathetics via pterygopalatine ganglion to lacrimal gland, mucous
glands of nose, palate and nasopharynx
Taste:
- Hard and soft palates
Main branches:
- Zygomatic and infraorbital
Other branches:
- Nasopalatine to nasal cavity
- Greater and lesser palatine to palate
- Alveolar to upper teeth
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Mandibular Nerve (V3)
Sensory:
- Lower face
- Temple, anterior 2/3 tongue
Carries:
- Parasympathetics via submandibular and otic ganglia to submandibular
- Sublingual
- Parotid glands
Branchiomotor:
- Muscles of mastication
- Tensors tympani and palati
Main Branches:
- Auricotemporal
- Buccal
- Mental
- Lingual
- Muscular
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Facial Nerve (VII)
Origin:
- Motor Nucleus of VII (motor)
- Nucleus solitarius (sensory)
- Gustatory nucleus (sensory)
- Superior salivatory and lacrimal nucleus (parasympathetic)
Component fibres:
- Motor
- Sensory
- Parasympathetic
Course:
- Fibres of motor nucleus loops over CN VI nucleus creating facial colliculus in
floor of 4th ventricle (internal genu)
- Passes through internal acoustic meatus to enter facial canal
- Widens to form geniculate ganglion (taste and salivation) on medial side of
middle ear, turns sharply (chorda tympani leaves)
- Emerge through stylomastoid foramen to supply muscles of facial expression
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Distribution:
- Motor to muscles of facial expression
 Stapedius
 Stylohyoid
 Posterior belly of digastric
- Taste from anterior 2/3 of tongue
- Skin of external acoustic meatus
- Sensory from mucous membrane of nasopharynx and palate
- Parasympathetic to:
 Lacrimal
 Nasal
 Palatine
 Submandibular
 Sublingual glands
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Vestibulocochlear Nerve (VIII)
Origin:
- Vestibular ganglion (semicircular canal) and end in vestibular nucleus
- Spiral ganglion (Organ of Corti) and end in cochlear nucleus
Course:
- Both pass with CN VII, from brainstem across posterior cranial fossa to internal
acoustic meatus
Component:
- Sensory
Function:
- Hearing
- Balance
- Equilibrium
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Glossopharyngeal (IX)
Origin:
- Nucleus ambigus (motor)
- Inferior salivatory
(parasympathetic)
- Tractus solitarius (sensory)
- Spinal nucleus of the trigeminal
(sensory)
Course:
- Passes across posterior cranial
fossa, through jugular foramen
and into neck supplying tonsil,
palate and posterior third of
tongue
Component:
- Motor
- Sensory
- Parasympathetic
Distribution:
- Stylopharyngeus (motor)
- Parotid gland (parasympathetic)
- Carotid body and sinus (carotid
sinus nerve- sensory)
- Oropharynx (pharyngeal0
sensory)
- Middle ear and inner ear (tympanic- sensory)
- Taste posterior 2/3 of tongue (lingual- special sensory)
- Tonsil and palate (tonsillar- sensory)
- External ear (sensory)
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Vagus Nerve (X)
Also called the pneumogastric nerve
Origin:
- Nucleus ambigus (motor)
- Dorsal nucleus of X (parasympathetic)
- Nucleus solitarius (sensory)
Component fibres:
- Motor
- Sensory
- Parasympathetic
Course of Vagus Nerve:
- Leaves skull through jugular foramen, passes within carotid sheath in neck
(giving off cardiac branches, and recurrent laryngeal nerves supplying vocal
cords)
- Continues through thorax supplying lungs and heart and then through
oesophageal opening to supply abdominopelvic organs via coeliac, hepatic,
renal and hypogastric plexuses.
Distribution of Vagus Nerve:
- Motor to pharyngeal constrictor muscles, intrinsic muscles of larynx, muscles of
palate
- Parasympathetic to smooth muscles of trachea, bronchi, GI tract, heart
- Sensory from tongue, pharynx, larynx, thoraco-abdominal viscera, auricle,
external auditory meatus, meninges of post cranial fossa.
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Accessory Nerve (XI)
Origin:
- Cranial root: Nucleus Ambigus
(motor)
- Spinal root: Accessory nucleus from
spinal cord (C1-C5)
Course:
- Spinal roots travel upward through
foramen magnum and join cranial
before passing through jugular
foramen
Component fibres:
- Motor
Function:
- Sternocleidomastoid
- Trapezius muscles
- Striated muscles of soft palate,
pharynx and larynx via fibres that
join CN X
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Hypoglossal Nerve (XII)
Origin:
- Hypoglossal nucleus (motor)
Course:
- Passes briefly across posterior cranial fossa skull through hypoglossal canal and
supplies motor fibres to tongue and most infrahyoid muscles
Component fibre:
- Motor
Function:
- Intrinsic muscles of the tongue
- Extrinsic muscles: genioglossus, styloglossus, hyoglossus
- Infrahyoid muscles
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