The cranial nerves are twelve pairs of nerves from the central nervous system. The cranial nerves are loosely based on their functions. In this summary, we discuss the nomenclature of the cranial nerves and supply some background information that might make it easier to understand the nerves and their function.

This summary should read alongside the complete articles for each of the cranial nerves:

Download our cranial nerves PDF summary table here.

You can also check out our Cranial Nerve Anatomy Quiz here.

Cranial nerves and cranial foramina diagram

Cranial nerves and cranial foramina diagram 1


Cranial nerve nuclei

The cranial nerve nuclei will be covered in more detail in each cranial nerve article. For now, it is worthwhile knowing that a nucleus refers to a collection of neuronal cell bodies within the central nervous system and they give rise to one of seven major types of fibres (below):

  • GSA – general somatic afferent – receive sensory information from the skin, skeletal muscles and joints
  • GVA – general visceral afferent – receive sensory information from the viscera (organs)
  • SSA – special somatic afferent – receive sensory information from the ectodermal retina, cochlear and vestibular apparatus
  • SVA – special visceral afferent – receive sensory information from the endodermal nose and tongue
  • GSE – general somatic efferent – provide motor innervation to skeletal muscles
  • GVE – general visceral efferent – provide secretomotor function to smooth muscle and glands
  • SVE – special visceral efferent – provide motor innervation to skeletal muscles of the pharyngeal arches

 

Afferent fibres carry sensory information back to the brain. Efferent fibres carry motor information away from the brain.


The cranial nerves themselves can be a complex area of anatomy to learn. We have broken the cranial nerves down to their bare essentials. The other cranial nerve articles in this series build on the information presented here.


Olfactory nerve (CN I)

  • CN I is the olfactory nerve
  • It provides special visceral afferent fibres for smell
  • It connects to the brain (not the brainstem!)
  • It passes through the cribriform plate of the skull

Optic nerve (CN II)

  • CN II is the optic nerve
  • It provides special somatic afferent fibres for vision
  • It connects to the brain (not the brainstem!)
  • It is the afferent limb for the pupillary light reflex
  • It passes through the optic canal of the skull

Oculomotor nerve (CNIII)

  • CNIII is the oculomotor nerve
  • It provides general somatic efferent and general visceral efferent fibres to the extraocular muscles and pupillary constrictor muscles respectively
  • The muscles are the levator palpebrae superioris, inferior oblique, and superior, medial and inferior recti
  • CN III damage causes a ‘down and out’ eye – you can deduce what its function is from this
  • It connects to the midbrain
  • It is the efferent limb for the pupillary light reflex
  • It passes through the superior orbital fissure of the skull

Trochlear nerve (CN IV)

  • CN IV is the trochlear nerve
  • It provides general somatic efferent to the extraocular superior oblique muscle
  • It assists in depressing and abducting the eye
  • It connects to the midbrain and is the only cranial nerve to leave the pontomesencephalic junction posteriorly
  • It passes through the superior orbital fissure of the skull

Trigeminal nerve (CN V)

  • CN V is the trigeminal nerve
  • It has three sensory nuclei:
    • Mesencephalicproprioception
    • Principallight touch and discrimination
    • Spinalpain, temperature, crude touch
  • It emerges from the pons
  • It is the afferent limb of the corneal reflex; CN VII is the bilateral efferent limb
  • It has three divisions (ophthalmic, maxillary and mandibular)

Division

Modality

Sensory function

Motor function

Foramen

Ophthalmic

V1

General Somatic Afferent

Above the lower eyelid

X

Superior orbital fissure

Maxillary

V2

General Somatic Afferent

Lower eyelid to the upper lip

X

Foramen rotundum

Mandibular

V3

General Somatic Afferent

Special Visceral Efferent

Below upper lip

Muscles of mastication

Foramen ovale

 


Abducens nerve (CN VI) 

  • CN VI is the abducens nerve
  • It originates in the pontomedullary region
  • It provides general somatic efferent fibres for eye abduction
  • It innervates the lateral rectus muscle
  • It passes through the superior orbital fissure of the skull

Facial nerve (CN VII)

  • CN VII is the facial nerve
  • It originates in the pontomedullary region
  • The facial nerve loops around the abducens nucleus
  • It passes through the internal auditory meatus and exits through the stylomastoid foramen
  • LMN facial nerve lesions cause upper and lower facial paralysis
  • UMN facial nerve lesions cause lower facial paralysis only
  • It provides many structures with innervation (shown in the table below)

General somatic afferent

Special visceral afferent

General visceral efferent

Special visceral efferent

Skin behind the ear

Taste to anterior 2/3 of the tongue

Parasympathetic to the lacrimal, sublingual and submandibular glands

Muscles of facial expression


Vestibulocochlear nerve (CN VIII)

  • CN VIII is the vestibulocochlear nerve
  • It originates in the pontomedullary region
  • It provides special somatic afferent fibres for hearing and balance
  • The cochlea transmits sound waves to mechanical ossicle movements to electrochemical action potentials
  • The vestibular apparatus detects changes in head motion
  • It passes through the internal auditory meatus and does not leave the skull

Glossopharyngeal nerve (CN IX)

  • CN IX is the glossopharyngeal nerve
  • It originates in the medulla oblongata
  • It draws fibres from the solitary nucleus (taste) and nucleus ambiguus (motor)
  • It draws more fibres from the inferior salivatory nucleus (parotid gland) and dorsal motor nucleus (DMX; pharyngeal sensation)
  • It passes through the jugular foramen
  • It provides many fibre types (shown in the table below)

General somatic afferent

Special visceral afferent

General visceral efferent

Special visceral efferent

Sensation from the posterior 1/3 of the tongue, pharynx

Taste to posterior 1/3 of the tongue

Parasympathetic to parotid glands

Motor to stylopharyngeus


Vagus nerve (CN X)

  • CN X is the vagus nerve
  • It originates in the medulla oblongata
  • Its major role is parasympathetic innervation of the viscera
  • The recurrent laryngeal nerve loops under the right subclavian artery and (left) aortic arch
  • It passes through the jugular foramen with CN IX and XI
  • It provides many fibre types (shown in the table below)

General somatic afferent

Special visceral afferent

General visceral afferent

General visceral efferent

Special visceral efferent

Skin around ear

Taste and sensation to the epiglottis

Sensory information to body viscera

Parasympathetic to glands of GI tract

Motor innervation to soft palate, pharynx and larynx


Accessory nerve (CN XI)

  • CN XI is the accessory nerve
  • It originates in the medulla oblongata and superior cervical cord region
  • It provides general somatic efferent fibres to the trapezius and sternocleidomastoid
  • It exits the spinal cord in the neck and enters the skull through the foramen magnum
  • It then leaves the skull by the jugular foramen with CNs IX and X

Hypoglossal nerve (CN XII)

  • CN XII is the hypoglossal nerve
  • It originates in the medulla oblongata
  • It provides general somatic efferent fibres for controlling tongue muscles
  • It exits the skull through the hypoglossal canal

Cranial nerve summary table 

You can download our cranial nerve summary table in PDF format here.

NERVE

MODALITY

FIBRE TYPE

FUNCTION

FORAMEN

I – Olfactory

Sensory

SVA

Smell

Cribriform plate

II – Optic

Sensory

SSA

Vision

Optic canal

III – Oculomotor

Motor

GSE, GVE

Extraocular muscles and eyelid elevator

Superior orbital fissure

IV – Trochlear

Motor

GSE

Superior oblique muscle

Superior orbital fissure

V – Trigeminal

Both

 

GSA

GSA

GSA, SVE

V1 – ophthalmic – face sensation

V2 – maxillary – face sensation

V3 – ophthalmic – face sensation

V1 – superior orbital fissure

V2 – foramen rotundum

V3 – foramen ovale

VI – Abducens

Motor

GSE

Lateral rectus

Superior orbital fissure

VII – Facial

Both

GSA, SVA, GVE, SVE

Muscles of facial expression + stapedius

Taste to the anterior 2/3 of the tongue

Tear and salivary ducts

Internal acoustic meatus

to stylomastoid foramen

VIII – Vestibulocochlear

Sensory

SSA

Balance – vestibular division

Hearing – cochlear division

Internal acoustic meatus

IX – Glossopharyngeal

Both

GSA, SVA, GVE, SVE

Taste for posterior 1/3 of the tongue

Sensation to pharynx

Innervates stylopharyngeus

Jugular foramen

X – Vagus

Both

GSA, SVA, GVA, GVE, SVE

Parasympathetic innervation to viscera above splenic flexure

Laryngeal muscles and palatoglossus

Jugular foramen

XI – Accessory

Motor

GSE

Motor control to SCM and trapezius

Jugular foramen

XII – Hypoglossal

Motor

GSE

Innervates tongue muscles except for palatoglossus

Hypoglossal canal


References

Reference texts

  • Sinnatamby, C. S. (2011). Last’s Anatomy, International Edition: Regional and Applied. Elsevier Health Sciences.
  • Moore, K. L., Dalley, A. F., & Agur, A. M. (2013). Clinically oriented anatomy. Lippincott Williams & Wilkins.
  • Nolte, J. (2002). The human brain: an introduction to its functional anatomy.
  • Snell, R. S. (2010). Clinical neuroanatomy. Lippincott Williams & Wilkins.

 

Reference images

  1. Patrick J. Lynch, medical illustrator [CC BY 2.5 (https://creativecommons.org/licenses/by/2.5)]. Modified by Dr Lewis Potter.

 

 

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