CRANIAL NERVES ANATOMY
Keele Neurology Society
Aziza Mohamed
Aisha Saleem
Introduction
• Twelve pairs of cranial nerves that originate
from the forebrain, brainstem and rostral
spinal cord.
• Form part of the peripheral nervous system –
similar properties to spinal nerves.
• Responsible for sensory, motor and/or
autonomic function in mainly* functional
regions of head and neck.
• Integral part of neurological examination.*
Cranial Nerve Function Overview
• Sensory, motor, autonomic or mixed.
• Can receive afferents or send impulses locally or
to regions such as thoracic and abdominal viscera
(e.g. CN X Vagus Nerve).
• Sensory - general somatic afferent, general
visceral afferent or special afferent.
• Motor - general somatic efferent or branchial
motor efferents.
• General or special visceral efferents are also
described as - Parasympathetic efferents.
Internal Cranium Base – Quick
Overview
Cranial Nerve Foramina
Cranial Nerve I:
Olfactory
SENSORY
- Special Afferent
• FORAMEN - Cribriform Plate of the
Ethmoid Bone
• Sensory – perception of smell.
Transmitted into the frontal lobe
from olfactory epithelium.
Cranial Nerve II:
Optic
SENSORY
- Special afferent
• FORAMEN - Optic canal
• Sensory – perception of vision;
detects and transmits light input
from optic disc at retina.
NB: Contralateral; optic chiasm at the sphenoid
wing involves decussation of the nerves into the
optic tract.
Cranial Nerve III:
Occulomotor
MOTOR – occulomotor
nerve palsy (down and out –
neurogenic ptosis causes
drooping of the eyelid due to
damage to CN III)
PARASYMPATHETIC
EFFERENTS
• FORAMEN - Superior Orbital Fissure
• Motor - Controls four of the six
extraoccular muscles ; superior
rectus, inferior rectus, medial rectus
and inferior oblique muscles. *Also
controls levator palpebrae
superioris (upper eyelid muscle)
• Parasympathetic efferent –
innervates sphincter pupillae for
pupil constriction and ciliary muscle
accommodation of lens at near
vision.
Cranial Nerve IV:
Trochlear
MOTOR
• FORAMEN - Superior Orbital Fissure
• Motor - controls the movement of
the superior oblique muscle of the
eye. Aids internal rotation of eye.
• *SO4 – Trochlear (CN IV)
Cranial Nerve V:
Trigeminal
SENSORY MOTOR -
• FORAMEN – Varied:
– V1 [opthalmic]- Superior Orbital Fissure
– V2 [maxillary]- Foramen Rotundum
– V3 [mandibular]- Foramen Ovale
• Sensory – touch, temperature
perception on different regions of face
(testing with soft/crude touch and
temperature).
• Motor - Muscles of mastication
particularly masseter and temporalis
Cranial Nerve VI:
Abducens
MOTOR
• FORAMEN – Superior Orbital Fissure
• Motor - Lateral rectus muscle of the
eye. Enables abduction of the eye.
• *LR6 – Abducens (CN VI)
Cranial Nerve VII:
Facial
SENSORY
MOTOR
PARASYMPATHETIC
EFFERENTS
• FORAMEN – Internal Acoustic
Meatus
• Sensory – special sensory is anterior
2/3 taste of tongue and external
acoustic meatus (including auricle)
• Motor – muscles of facial
expressions [5 branches] and neck
muscles.
• Parasympathetic – submandibular,
sublingual and lacrimal salivary
glands . Also innervates mucous
membranes of nasal cavity.
1. Temporal
2. Zygomatic
3. Buccal
4. Maxillary
5. Cervical
Cranial Nerve VIII:
Vestibulocochlear
SENSORY - special afferent
• FORAMEN – Internal Acoustic
Meatus
• Sensory – special sensory function:
– Vestibular division responsible for
balance
– Cochlear division responsible for
hearing
Cranial Nerve IX:
Glossopharyngeal
SENSORY
MOTOR
PARASYMPATHETIC
EFFERENTS
• FORAMEN – Jugular Foramen
• Sensory – input from the carotid
body and sinus (detects changes in
PCO2 and pressure). Taste in
posterior 1/3 of tongue.
• Motor – controls stylopharyngeal
muscle for swallowing.
• Parasympathetic efferent innervates parotid salivary gland
Cranial Nerve X:
Vagus
SENSORY
MOTOR - dysphagia (often
seen in patients who’ve
suffered from stroke)
PARASYMPATHETIC
EFFERENTS
• FORAMEN – Jugular Foramen
• Sensory – varied:
– Sensation in larynx, laryngopharynx,
including parts of the external acoustic
meatus.
– Sensory from the aortic body and aortic
sinus, thoracic and abdominal viscera.
– Taste in the epiglottis and upper pharynx
• Motor – innervates only one tongue
muscle, varied muscles in pharynx and
larynx. – Aid in speech and swallowing
• Parasympathetic efferents – innervates
smooth muscles and glands in throat
region, thoracic viscera and abdominal
viscera upto the midgut. (2/3 of Transverse
Colon)
Cranial Nerve XI:
Accessory
MOTOR -
• FORAMEN - Jugular Foramen
• Motor – innervates
sternocleidomastoid muscle and
trapezius muscles of neck and
shoulder region. Aids rotation and
flexion of head and neck; shrugging
move scapula and support arm.
Cranial Nerve XII:
Hypoglossal
MOTOR - “the tongue licks
the wound” (damage to the
hypoglossal nerve leads to
deviation of tongue to
ipsilateral side where injury
occurred)
• FORAMEN - Hypoglossal Canal
(lateral to Foramen Magnum)
• Motor – control of tongue muscles;
including pharynx and larynx
(muscles of speech and swallowing).
Origin of Cranial Nerves
•
•
•
•
•
•
•
•
•
•
•
•
CN I – Olfactory Bulb (inf. surface of Frontal Lobe)
CN – Retina
CN III – Midbrain
CN IV – Midbrain
Majority of cranial nerves
CN V – PONS
originate from the
CN VI – PONS
brainstem (CN III – CN XII
[excluding CN XI])
CN VII – PONS
CN VIII – PONS
CN IX – Medulla
CN X – Medulla
CN XI – Spinal Cord*
CN XII – Medulla
Cranial Nerve Nuclei*
*Spinal Accessory Nerve XI – Originates from spinal cord directly
Mnemonics
• Oh Once One Takes The Anatomy Finals Very
Good Vacations Are Heavenly.
• Some Say Marry Money, But My Brother Says
Big Business Makes Money.
• Carl Only Swims South. Silly Roger Only Swims
In Infiniti Jacuzzis. Jane Just Hitchhikes.
• To Zanzibar By Motor Car* [5 Branches of Facial Nerve]
Useful Websites & Resources
• Yale University: http://www.yale.edu/cnerves/
• fastbleep: http://www.fastbleep.com/medical-notes/neuroand-psych/2/95/610
• UBC (University of British Colombia):
http://www.neuroanatomy.ca/
• TeachMeAnatomy: www.teachmeanatomy.co.uk
• Mnemonics:
file:///S:/Downloads/List%20of%20mnemonics%20for%20the
%20cranial%20nerves.pdf
References
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•
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Mike Mahon – Cranial Nerve Neuroanatomy Lecture
Neuroanatomy Illustrated
Gray’s Anatomy for Students
Bear’s Neuroscience
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