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Cranial Nerves

The Cranial Nerves are nerves that originate from the brain stem.

They are a very specialized set of nerves with an important role in the movement of the eyes, smell, and more.

There are 12 overall cranial nerves and they control a variety of functions both motor or sensory

Motor is the movement of a muscle [Efferent]

Sensory is the sight, touch, or smells of the senses that are transmitted to the brain  [Afferent]

Many cranial nerves are either Motor  [Efferent] or Sensory [Afferent] but some are both

Cranial Nerves:

I – Olfactory or smell  [Afferent]

–  Transmits sense of smell

II – Optic or vision [Afferent]

–  Transmits visual information from eye to brain

III – Oculomotor or movement of eyeball  [Efferent]

–  Innervates levator palpebrae of the eye
–  Innervates superior rectus of the eye
–  Innervates medial rectus of the eye
–  Innervates inferior rectus of the eye
–  Innervates inferior oblique of the eye
–  Affects the majority of eye movement
–  The exceptions are with Cranial nerves IV and VI

IV – Trochlear or muscles of eyeball  [Efferent]

–  Innervates superior oblique muscle of the eye
–  Allows for movements of the eye including: lateral, depresses, and intorts

V – Trigeminal   [Afferent]  and  [Efferent]

–  V1 – ophthalmic [Afferent]
–  V2 – maxillary  [Afferent]
–  V3 – mandibular  [Afferent] and [Efferent]
–  Receives sensation from the face.
–  Innervates facial muscles for mastication [chewing]

VI – Abducens or muscles of eyeball  [Efferent]

–  Innervates the lateral rectus of the eye
–  Affects the abduction of the eye

VII – Facial   [Afferent] and  [Efferent]

–  Motor innervation to the muscles of the face
–  Allows for facial expressions
–  Receives senses of taste from the anterior 2/3 of the tongue
–  Affects secretion of the salivary glands [except parotid]

VIII – Vestibulocochlear  [Afferent]

–  Senses Gravity
–  Senses Sound
–  Senses Rotation
–  Essential for balance and movement

IX – Glossopharyngeal  [Afferent]  and  [Efferent]

–  Receives taste from the posterior 1/3 of the tongue
–  Affects secretion of the Parotid gland
–  Affects some sensation of the Tonsils

X – Vagus [Afferent]  and  [Efferent]

–  Supplies motor innervation to most laryngeal and all pharyngeal muscles
–  Controls muscles for voice
–  Helps control soft palate

XI – Accessory or spinal   [Efferent]

–  Controls sternocleidomastoid
–  Controls trapezius muscles
–  Helps with shrugging shoulders

XII – Hypoglossal or tongue  [Efferent]

–  Provides motor innervation to the muscles of the tongue
–  Important for Speech
–  Important for Swallowing

Check out the Video of the Cranial Nerve Examination