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