Download Cranial Nerves

CRANIAL NERVES
Bryan Sackey
Pharmacy Biomedical Preview Program
Summer 2012
[email protected]
At the end of this presentation, participants
should be able to discuss the:
•  Location and innervation of all twelve cranial nerves
•  Categorization of cranial nerves
•  Sensory
•  Motor
•  Mixed
•  Basic function of cranial nerves
•  Some clinical manifestations of cranial nerve damage
Cranial Nerves
•  Humans possess 12 cranial nerves which emerge from
the brain
•  All cranial nerves arise from brain stem except the 1st and 2nd
(Olfactory and Optic nerve)
•  1st and 2nd arise from cerebrum
•  Categorized as either sensory, motor or mixed (both sensory and
motor)
•  3 sensory
•  5 motor
•  4 mixed
Cranial nerve I: Olfactory Nerve
•  Arises from Olfactory epithelium of cerebrum
•  Olfactory bulb
•  Enters the nasal cavity
•  Solely Sensory function
•  Functions in the special sense of smell
•  Clinical Implications
•  Anosmia
Cranial Nerve II: Optic Nerve
•  Arises from retina of eye
•  Pass through optic canal and converge at optic chiasm then to
visual cortex
•  Solely Sensory function
•  Carriers afferent impulses for vision
•  Clinical implications:
•  Blindness
•  Tunnel vision
Cranial Nerve III: Oculomotor nerve
•  Arises from the midbrain
•  Enters Superior orbital fissure (to eye)
•  Solely Motor function
•  Innervates 5 extraocular muscles of the eye
•  Superior rectus – rotates eye upward
•  Medial rectus – rotates eye medial
•  Inferior rectus – rotates eye downward
•  Inferior oblique – rotates eye upward and laterally
•  Levator palebrae superioris – lifts up eyelids
•  Clinical implications
•  External strabismus
Cranial Nerve IV: Trochlear Nerve
•  Arises from midbrain
•  Enters superior orbital fissure
•  Motor function
•  Innervates superior oblique muscle
•  Moves eye downward and medially
•  Clinical Manifestation
•  Damage to nerve causes eye to rotate laterally
note: this is
the right eye
with the nose
to the left of it
Cranial Nerve V: Trigeminal Nerve
•  Arises from the pons
•  Has BOTH motor and Sensory functions (mixed nerve)
•  Composed of 3 branches
•  V1: Ophthalmic branch – superior orbital fissure
•  V2: Maxillary branch – foramen rotundum
•  V3: Mandibular branch – foramen ovale
•  V1 and V2 conveys sensory impulses from various parts
of the face and V3 is responsible for mastication (motor)
•  Clinical Implications
•  Herpes Zoster
•  Tic Douloureax
Cranial Nerve VI: Abducens Nerve
•  Arises from the pons
•  Enters superior orbital fissure
•  Solely Motor function
•  Innervates lateral rectus muscle of the extraocular muscle in eye
•  pulls eye laterally (abducts eye  abducens!)
•  Clinical Implications
•  Internal strabismus
Cranial Nerve VII: Facial Nerve
•  Arises from pons
•  Enters through stylomastoid foramen to the lateral aspect
of face
•  BOTH motor and sensory function (mixed nerve)
•  Motor functions involves facial expression
•  Sensory function is taste from anterior 2/3 of tongue
•  Clinical Implications
•  Bell’s Palsy
•  paralysis of facial muscle leading to asymmetrical facial expression
Cranial Nerve VIII: Vestibulocochlear
•  Arise from pons
•  Enter hearing and equilibrium apparatus of middle ear
•  Sensory function
•  Hearing and balancing
•  Clinical implications
•  Deafness
•  Tinnitis
•  Vertigo
Cranial Nerve IX: Glossopharyngeal
•  Arises from medulla
•  Enters jugular foramen and runs to throat
•  BOTH motor and sensory function
•  Motor function innervates part of tongue for movement and salivary
gland
•  Supplies sensory fibers to posterior 1/3 of tongue
•  Helps taste and swallow food
•  Clinical implications
•  Dysphagia
•  Swallowing difficulty
Cranial Nerve X: Vagus Nerve
•  Arises from medulla
•  travels through jugular foramen
•  Only cranial nerve that extends beyond the head and
neck
•  BOTH motor and sensory function
•  Motor functions are parasympathetic fibers to the heart, lungs,
digestion, and visceral organs
•  Involved in swallowing and speech
•  Sensory functions is taste
•  Clinical implications
•  Responsible for many visceral functions so if damaged may lead to
problems with visceral organs
•  Dysphagia
Cranial Nerve XI: Accessory Nerve
•  Arises from Medulla
•  Enters through foramen magnum
•  Solely Motor function
•  Innervates sternocliedomastoid muscle and trapezius muscle
•  Responsible for head movement and neck rotation
•  An accessory to the motor functions of Vagus nerve by innervating
larynx, pharynx, and soft palate
•  Clinical manifestations
•  Inability to shrug
Cranial Nerve XII: Hypoglossal Nerve
•  Arise from Medulla
•  Enters through hypoglossal canal
•  Solely Motor function
•  Innervates both intrinsic and extrinsic muscles of tongue
•  Involved in protraction of tongue
•  Involved with swallowing and speech
•  Clinical implications
•  Deviation of tongue
Summary
•  3 sensory
•  Olfactory (CN I), Ophthalmic (CN II), Vestibulocochlear (CN VIII)
•  5 motor
•  Oculomotor (CNIII), Trochlear (CN IV), Aducens (CN VI), Accessory
(CN XI), Hypoglossal (CN XII)
•  4 Mixed (both motor and sensory)
•  Trigeminal (CN V), Facial (CN VII), Glossopharyngeal (CN IX), Vagus
(CN X)
•  3 involved in taste
•  Facial (CN VII), Glossopharyngeal (CN IX), Vagus (X)
•  2 involved in speech
•  Vagus (CN X), Hypoglossal (CN XI)
•  3 involved in eye movement
•  Oculomotor (CN III), Trochlear (CN IV), Abducens (CN IV)
•  1 leaves head and neck area
•  Vagus nerve (CN X)