Mod 4: Lecture 2: Overview of Cranial Nerves Flashcards
Brain Stem
- Midbrain
- Pons
- Medulla
Mnemonic for the 12 pairs of Cranial Nerves
- Oh Once One Takes The Anatomy Final, Very Good Vacations Are Heavenly.
Cranial Nerves: I - IV
I. Olfactory
II. Optic
III. Oculomotor
IV. Trochlear
Cranial Nerves: V - VIII
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
Cranial Nerves: IX - XII
IX. Glossopharyngeal
X. Vagus
XI. (Spinal) Accessory
XII. Hypoglossal
Cranial Nerves Originating in the Diencephalon-Brainstem (Can’t read slide, see video)
I. Olfactory
II. Optic
Cranial Nerves Originating in the Midbrain
III. Oculomotor
IV. Trochlear
Cranial Nerves Originating in the Pons
V. Trigeminal
VI. Abducens
VII. Facial
VIII. Vestibulocochlear
Cranial Nerves Originating in the Medulla
IX. Glossopharyngeal
X. Vagus
XI. Accessory
XIII. Hypoglossal
Cranial Nerves are part of the __1__ nervous system and pass through the skull via __2__ or __3__.
- peripheral
- foramina
- fissures
Cranial Nerve Classification
- Sensory: vision, smell, touch
- Motor: somatic and visceral
- Both
CN I. Olfactory Nerve
- sensory
- olfactory bulb is on the cribriform plate
- fibers of olfactory nerves extend down into the nasal passages by the nasal conchae
CN II: Optic
- sensory
- info from the right and left visual field goes to both eyes and both optic nerves
- at the optic chiasma, the right and left optic nerves cross
- — info from the right visual field from both eyes goes to the left brain
- — same for info from the left visual field
III. Occulomotor
- motor
- innervates the elevator of the upper eyelid
- — levator palpebrae superioris
- innervates 4 of 6 muscles responsible for movement of the eyeball
- — rectus superior, rectus inferior, rectus medial and inferior oblique
- — does not innervate the superior oblique or the rectus lateral
- parasympathetic motor fibers to the sphincter muscle of the iris
- — pupil constriction
Isolated movements of the eyeball
- elevation
- depression
- adduction: toward midline/nose
- abduction: away from midline
- internal/medial rotation
- — intorsion
- — 12 o’clock position moves clockwise (toward nose)
Direction of pull and action of the extraocular eye muscles if they were to contract in isolation….
- Superior rectus
- Inferior Rectus
- Medial Rectus
- Lateral Rectus
- Pulls upward
- elevation
- — you look up
- Pulls upward
- pulls downward
- depression
- — you look down
- pulls downward
- pulls inward to the nose
- adduction
- — when both do it, you go cross eyed
- pulls inward to the nose
- pulls outward, to the lateral side, away from the body
- abduction
- — you glance sideways
- pulls outward, to the lateral side, away from the body
Eye Muscles: Superior Oblique
- Attachments
- Action
- Innervation
- posterior and superior to the horizontal axis
- rotate clockwise, from the top to the nose
- intorsion (internal/medial rotation)
- depression
- — you roll your eyes
- — bc of attachment, it lifts up the back of the globe, therefore the rest turns down (depresses)
- rotate clockwise, from the top to the nose
- IV. Trochlear
Eye Muscles: Inferior Oblique
- Attachments
- Action
- Innervation
- posterior and inferior to the horizontal axis
- rotate counterclockwise, from the bottom to the nose
- extorsion (external/lateral rotation)
- elevation
- — you roll your eyes
- — bc of attachment, it pulls down the back of the globe, and therefore pushes the rest or the eye up (elevates)
- rotate counterclockwise, from the bottom to the nose
- III. Occulomotor
Innervation of the lateral rectus
- CN VI. Abducens
- all other rectuses are CN III. Occulomotor
Pupillary Light Reflex
- automatic constriction of pupils upon exposure to bright light
- light entering the eye travels along the optic nerve to the midbrain to cause pupillary constriction
- — through the visceral motor and short component of the occulomotor
Occulomotor Palsy
- ptosis, pupil dilation
- see video
Abducens Lesion
- adjacent nerve injury
- abducens goes to the lateral rectus
- — abducens stops working, eye (pupil/iris) falls to one side instead of being in the middle
- see video
IV. Trochlear
VI. Abducens
IV. - motor
- superior oblique of the eye
VI. - motor
- lateral rectus of the eye
V. Trigeminal
- mixed
- V1. Ophthalmic: above eyes
- V2. Maxillary: upper lip and cheek
- V3. Mandibular:
- — motor to muscles of mastication
- — sensory branches to lower jaw and side of face in front of ears
VII. Facial
- mixed
- Motor
- — supply to muscles of facial expression
- — autonomic innervation to glands of the head
- Sensory
- — taste to anterior 2/3 of tongue
- 6 branches
6 branches of the Facial Nerve (CN VII)
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
- Post Auricula
Bell’s Palsy
- VII. Facial nerve
- facial paralysis resulting from damage to the facial nerve
- cause is often unknown
- — may be related to trauma or infection
- symptoms may begin suddenly and reach their peak within 48 hours
- symptoms range in severity from mild weakness to total paralysis
- — weakness in muscles of facial expression (upper and lower)
- most people recover in 2 weeks to 6 months
VIII. Vestibulocochlear
- sensory
- goes from medulla to the cochlea and vestibular apparatus in the internal ear
- carried afferent fibers for hearing and balance
IX. Glossopharyngeal
- mixed
- motor
- — stylopharygeus muscle of pharynx
- — parasympathetic: to parotid gland - salivation
- sensory
- — taste from posterior 1/3 of tongue
- — chemo and baroreceptors for cardiovascular regulation
X. Vagus
- mixed
- motor
- — to remaining pharyngeal muscles and laryngeal muscles
- — parasympathetic: heart, lungs, and digestive tract
- sensory
- — afferent from chemo and baroreceptors of afferent arch
- — sensation from pharynx, larynx, trachea, and thoracic and abdominal viscera
XI. (Spinal) Accessory
- motor
- has spinal and cranial roots
- axons leave the cranium to innervate the trapezius and sternocleidomastoid muscles
Clinical Correlation: accessory nerve injury
- weakness in the fibers of the trapezius can be caused by compression of the accessory
XII. Hypoglossal
- motor
- to muscles of the tongue
Clinical correlation: hypoglossal injury
- hypoglossal nerve function is tested by asking the patient to protrude her tongue
- if the hypoglossal nerve is injured, the tongue deviates toward the side of the lesion
- — toward the weak side
