Overview of the Cranial Nerves

There are 12 pairs of cranial nerves (CNs), which run from the brain to various parts of the head, neck, and trunk. The CNs can be sensory or motor or both. Some CNs are involved in special senses, like vision, hearing, and taste, and others are involved in muscle control of the face. The CNs are named and numbered in Roman numerals according to their location, from the front to the back of the brain.

Last update:

Table of Contents

Share this concept:

Share on facebook
Share on twitter
Share on linkedin
Share on reddit
Share on email
Share on whatsapp

General Features

Table: Overview of the 12 cranial nerves (CNs)
NerveCNFunctionType
OlfactoryIOlfaction (smell)Sensory
OpticIIVisionSensory
OculomotorIII
  • Eye movement
  • Pupillary constriction
  • Accommodation
  • Eyelid opening
Motor
TrochlearIVEye movement (superior oblique muscle)Motor
TrigeminalV
  • Facial sensation
  • Mastication
Both
AbducensVIEye movement (lateral rectus muscle)Motor
FacialVII
  • Facial movements
  • Taste from anterior ⅔ of tongue (chorda tympani)
  • Lacrimation
  • Salivation
  • Eyelid closing
  • Auditory reflex
Both
VestibulocochlearVIII
  • Hearing
  • Balance
Sensory
GlossopharyngealIX
  • Taste and sensation of posterior ⅓ of tongue
  • Monitoring of carotid body and sinus chemoreceptors and baroreceptors
  • Elevation of pharynx/larynx
Both
VagusX
  • Taste from supraglottic region
  • Swallowing
  • Soft palate elevation
  • Speech
  • Cough reflex
  • Parasympathetic innervation to thoracoabdominal viscera
  • Monitoring aortic arch chemoreceptors and baroreceptors
Both
AccessoryXI
  • Head turning
  • Shoulder shrugging
Motor
HypoglossalXIITongue movementsMotor
Table: Mnemonics to remember the cranial nerves
Cranial nerveMnemonic 1Mnemonic 2
OlfactoryOohOh
OpticOohOnce
OculomotorOohOne
TrochlearToTakes
TrigeminalTouchThe
AbducensAndAnatomy
FacialFeelFinal
VestibulocochlearVeryVery
GlossopharyngealGoodGood
VagusVelvetVacations
AccessoryAhAre
HypoglossalHeavenHeavenly
Roots of the cranial nerves

The 12 cranial nerves as they exit from the brain

Image: “Roots of the cranial nerves” by Phil Schatz. License: CC BY 4.0

Location and Function

Cerebral origin

  • CN I (olfactory)
    • Sensory function: olfaction (smelling)
    • Exits the skull via the cribriform plate
  • CN II (optic)
    • Sensory function: transmission of visual information from the retina to the vision centers of the brain
    • Exits the skull via the optic canal

Midbrain

  • CN III (oculomotor)
    • Motor function: movement of the upper eyelid and eye
    • Parasympathetic function:
      • Accommodation (ability to cross eyes)
      • Constriction of the pupil via the iris sphincter muscle 
      • Dilation of the pupil via the iris dilator muscle
    • Exits the skull via the superior orbital fissure
  • CN IV (trochlear)
    • Motor functions: 
      • Eye movement
      • Innervation of the superior oblique muscle 
    • Exits the skull via the superior orbital fissure

Pons

  • CN V (trigeminal) has 3 branches:
    • Ophthalmic nerve (V1):
      • Sensory innervation of the forehead, eyes, and nose
      • Exits the skull via the superior orbital fissure
    • Maxillary nerve (V2):
      • Innervation of the lower eyelid, teeth, nasal cavity, gums of the upper jaw, palate, and tonsils 
      • Autonomic innervation of the lacrimal and nasal glands
      • Exits the skull via the foramen rotundum
    • Mandibular nerve (V3) 
      • Motor innervation of the muscles of mastication
      • Sensory supply of the teeth, gums of the lower jaw, buccal mucosa, dorsum of the tongue, and external acoustic meatus
      • Exits the skull via the foramen ovale
  • CN VI (abducens)
    • Motor function: abduction of the eyes
    • Exits the skull via the superior orbital fissure
  • CN VII (facial)
    • Motor functions: 
      • Innervation of the entire facial musculature
      • Eyelid movement and closing of the eye via the orbicularis oculi muscle 
      • Movement and closing of the mouth via the orbicularis oris muscle 
      • Precise adjustment of the auditory ossicles via the stapedius muscle
      • Movement of the mandible via the mentalis muscle 
    • Sensory and parasympathetic functions: 
      • Sense of taste in the anterior ⅔ of the tongue (chorda tympani branch of the facial nerve)
      • Innervation of the 3 large salivary glands, lacrimal glands, and nasal glands 
    • Exits the skull via the stylomastoid foramen and internal auditory meatus
  • CN VIII (vestibulocochlear)
    • Vestibular nerve: 
      • Regulation of the hair cells of the organ of Corti for the adjustment of spatial position 
      • Transmission of impulses for the sense of balance 
    • Cochlear nerve: 
      • Regulation of the hair cells of the organ of Corti for the adjustment of sensitivity regarding sound waves
      • Transmission of impulses for hearing
    • Exits the skull via the internal auditory meatus

Medulla

  • CN IX (glossopharyngeal) 
    • Sensory functions: 
      • Innervation of the mucosa of the middle ear, mastoid, and eardrum 
      • Supply of the velum, including the palatine tonsils and posterior ⅓ of the tongue 
      • Taste and somatic perception (touch, pain, and temperature) of the posterior ⅓ of the tongue 
      • Proprioception of swallowing musculature 
      • Blood pressure regulation 
      • Monitoring of O2 and CO2 content of blood for control of ventilation 
    • Motor functions: 
      • Innervation of the palate and the muscles of the pharynx
      • Dilation of the pharynx during swallowing and speaking 
    • Parasympathetic functions: 
      • Stimulation of salivation
      • Carotid body contains chemoreceptors that monitor blood O2 content as well as pressure receptors that are important for the regulation of blood pressure
    • Exits the skull via the jugular foramen
  • CN X (vagus)
    • Sensory functions: 
      • Taste and sensation in the epiglottis and the pharynx 
      • Blood pressure regulation 
      • Monitoring of O2 and CO2 content in blood for control of ventilation 
      • Sensation in thoracic and abdominal organs 
    • Motor functions:
      • Swallowing 
      • Coughing 
      • Speech 
    • Parasympathetic functions: 
      • Contraction and relaxation of the smooth muscles of the GI tract 
      • Reduction of the HR 
      • Secretion of digestive juices
    • Exits the skull via the jugular foramen
  • CN XI (spinal accessory) 
    • Motor function: movements of the head and shoulders
    • Exits the skull via the jugular foramen
  • XII (hypoglossal)
    • Motor function: movements of the tongue
    • Exits the skull via the hypoglossal canal

Mnemonic to remember the functions of the cranial nerves

Table: Functions of the cranial nerves
CNSensory, Motor, or Both
ISome
IISay
IIIMarry
IVMoney
VBut
VIMy
VIIBrother
VIIISays
IXBig
XBrains
XIMatter
XIIMore

Clinical Relevance

  • Acoustic neuroma (Schwannoma): benign tumor of Schwann cells that involve the CNs within the cranium. Acoustic neuroma most frequently affects CN VIII, but it can also impact CN VII because of its location in the cerebellopontine angle. The condition often presents with hearing loss and tinnitus. Treatment is with surgical resection.
  • Herpes zoster ophthalmicus: subtype of shingles that impacts the trigeminal nerve. Shingles is due to the varicella zoster virus (VZV). After exposure, VZV remains latent in the dorsal root ganglion, where it lives in equilibrium with the healthy immune system. With age, and immune system decline, VZV can reactivate and cause a painful, vesicular rash called herpes zoster. When herpes zoster affects the trigeminal nerve, it can involve the cornea of the eye.
  • Trigeminal neuralgia: chronic pain disorder that affects the trigeminal nerve. Trigeminal neuralgia can be due to compression caused by the superior cerebellar artery, tumors, aneurysms, or infarcts. The condition typically presents with exquisite pain that is out of proportion to the external stimulus in the regions supplied by the trigeminal nerve.

References

  1. Park, J.K., Vernick, D.M. (2020). Vestibular schwannoma (acoustic neuroma). UpToDate. Retrieved May 23, 2021, from https://www.uptodate.com/contents/vestibular-schwannoma-acoustic-neuroma?search=acoustic%20neuroma
  2. Martin, K.A. Patient education: Vestibular schwannoma (acoustic neuroma). UpToDate. Retrieved May 23, 2021, from https://www.uptodate.com/contents/vestibular-schwannoma-acoustic-neuroma-the-basics?search=acoustic%20neuroma
  3. Kutz, J.W. (2020). Acoustic neuroma: Practice essentials, history of the procedure, epidemiology. Medscape. Retrieved May 23, 2021, from https://emedicine.medscape.com/article/882876-overview
  4. Albrecht, M.A., Levin, M.J. (2021). Epidemiology, clinical manifestations, and diagnosis of herpes zoster. UpToDate. Retrieved April 18, 2021, from https://www.uptodate.com/contents/epidemiology-clinical-manifestations-and-diagnosis-of-herpes-zoster
  5. Albrecht, M.A. (2020). Diagnosis of varicella zoster virus infection. UpToDate. Retrieved April 18, 2021, from https://www.uptodate.com/contents/diagnosis-of-varicella-zoster-virus-infection
  6. Albrecht, M.A. (2020). Treatment of herpes zoster in the immunocompetent host. UpToDate. Retrieved April 18, 2021, from https://www.uptodate.com/contents/treatment-of-herpes-zoster-in-the-immunocompetent-host

Study on the Go

Lecturio Medical complements your studies with evidence-based learning strategies, video lectures, quiz questions, and more – all combined in one easy-to-use resource.

Learn even more with Lecturio:

Complement your med school studies with Lecturio’s all-in-one study companion, delivered with evidence-based learning strategies.

🍪 Lecturio is using cookies to improve your user experience. By continuing use of our service you agree upon our Data Privacy Statement.

Details