Cranial Nerves I Flashcards
Cranial Nerve Modalities: Somatomotor
- GSE
- Skeletal mm. of tongue and eye (extrinsic)
Cranial Nerve Modalities: Visceromotor
- GVE
- Only parasympathetic travel with CN to smooth and cardiac mm.
- Visceral glands, salivary and lacrimal glands, mucus glands and membranes
Cranial Nerve Modalities: Branchiomotor
- SVE
- Skeletal mm. of the branchial arches
- e.g.- mm of mastication, facial expression, pharynx (swallowing), larynx (speech)
Cranial Nerve Modalities: Somatosensory
- GSA
- Touch, temp., pain receptors in skin, oral and nasal cavities, and pharynx
Cranial Nerve Modalities: Viscerosensory
- GVA
- Stretch receptors of the gut
- Baroreceptors of the carotid and aortic bodies
- Chemoreceptors of gut and carotid body
Cranial Nerve Modalities: Special Sensory
- SSA- vision, hearing, and balance
- SVA- smell and taste
Innervation Chart

CN I
- Olfactory N.
- SVA
- Sensation of olfaction (smell)
- Not a true nerve, but a nerve tract (composed of 2o sensory neurons in olfactory bulb)
- 1o neurons are receptor cells in epithelial lining nasal cavity, axons pierce cribriform plate of ethmoid bone
- CN I is outgrowth of cerebrum
The Orbit
- Bony margin (7 bones)
- Frontal
- Ethmoid
- Lacrimal
- Maxillary
- Palatine
- Sphenoid
- Zygomatic
The Orbit: Contents
- Eyeball
- Extraoccular muscles
- Nerves
- CN II, III, IV, V1, V2, and VI
- Sympathetic nerves in ciliary nerves
- Vasculature: opthalmic artery, retinal artery, superior and inferior opthalmic veins
- Lacrimal gland
- Extraoccular fat
Innervation of the Orbit
- Special sensory (SSA): (CN II) retina
- Somatosensory (GSA): (CN V1) eyeball
- Somatomotor (GSE): (CN III, IV, VI) 6 extra-ocular muscles (4 rectus, 2 oblique), and levator palpebrae superioris
- Visceromotor (GVE): (CN III, VII) 3 intrinsic muscles (sphincter pupillae, dilator pupillae, ciliary muscles, CN III), superior tarsal muscles (sympathetic), lacrimal gland (CN VII)
The Eyeball
- cornea: transparent covering to anterior eye
- iris: controls pupillary diameter, determines eye color
- pupil: a hole in the center of the iris that allows light in
- lens: refracts light to focus image on retina
- ciliary body: controls the shape of the lens
- sclera: connective tissue covering to eye
- retina: detects images through photoreceptors, sends signal to CN II
CN II
- Optic N.
- SSA
- Not a true nerve, but a nerve tract (composed of axons of 2o sensory neurons)
- 1o neurons are receptor cells (photoreceptors=rods and cones) in retina
- Outgrowth of diencephalon
Optic nerve between
Chiasm and retina
Optic chiasm
Where optic n. fibers from the nasal side of the retina (lateral visual field) cross over to the contralateral side of the brain
Optic tract
Between chiasm and thalamus
Anopsia
loss of total visual field in one eye due to lesion of optic nerve
Heteronymous hemianopsia
- loss of 1/2 visual field on different side of the eyes
- temporal hemianopsia: optic chiasm lesion
Homonymous hemianopsia
loss of 1/2 visual field on same side of the eyes due to optic tract lesion
CN III
- Oculomotor N.
- GSE
- Somatomotor
- Superior, medial, and inferior rectus mm.
- Inferior oblique m.
- Levator palpebrae superioris m.
- GVE
- Visceromotor
- CN III carries pre-ganglionic parasympathetic fibers from the brain to the ciliary ganglion
- Post-ganglionic parasympathetics travel via the short ciliary n. to the eyeball
- Constrictor pupillae m., ciliary m.
CN III: Oculomotor N.: Somatomotor function (GSE)
- Superior rectus m.
- Medial rectus m.
- Inferior rectus m.
- Inferior oblique m.
Upper eyelid
- CN V1- opthalmic n.
- Somatosensory (GSA)
- CN III- oculomotor n.
- Somatomotor (GSE)
- Levator palpebrae superioris m.
- Sympathetic nervous system
- Visceromotor (GVE)
- Superior tarsal muscle
CN III: Oculomotor n.: Visceromotor (GVE) Component
- Pupillary light reflex
- Pupil contraction
- Accomodation reflex
- Changing focus between near and far objects
CN III: Ciliary ganglion
- parasympathetic
CN III: Short ciliary n.
- Parasympathetic (CN III)
- Sympathetic
- Sensory (CN V1)
CN III: Long ciliary n.
- Sympathetic
- Sensory (CN V1)
CN III: Pupillary Light Reflex
- optic n. (CN II) senses light
- oculomotor n. (CN III) constricts pupils
- short ciliary nn.
- constrictor pupillae mm.
- direct (ipsilateral) and consensual (contralateral) responses
- Sympathetic nerves dilate pupils
- short and long ciliary nn.
- dilator pupillae mm.
Pupillary Constriction Diagram

CN III: Acommodation reflex
- Changing focus between near and far objects
- Works via change in lens shape and pupil size
- Contraction of ciliary m. puts slack on the suspensory ligametns, rounds the lens, and causes the eye to focus on near objects
Ptosis
- drooping eyelid
- Horner’s syndrome
- Sympathetic nerve damage
- Ptosis + miosis (constricted pupil)
- Loss of superior tarsal m.
- Unopposed constrictor pupillae m.
- Oculomotor Palsy
- Motor and parasympathetic nerve damage
- Ptosis and mydriasis (dilated pupil)
- Loss of levator palpebrae superioris m.
- Unopposed dilator pupillae m.
CN IV
- Trochlear n.
- GSE
- Somatomotor
- Superior oblique m.
CN VI
- Abducens n.
- GSE
- Somatomotor
- Lateral rectus m.
Extra-Ocular Palsies
- CN III Palsy: eye rotated “down and out”, due to unopposed superior oblique (CN IV)
- CN IV Palsy: eye rotated up and in due to unopposed superior rectus (CN III) patient presents with “head tilt” to force even gaze
- CN VI Palsy: eye adducted due to unopposed medial rectus (CN III)
CN V
- Trigeminal nerve
- GSA, SVE
- Three branches
- CN V1: opthalmic n. (GSA)
- CN V2: maxillary n. (GSA)
- CN V3: mandibular n. (GSA, SVE)
CN V: Somatosensory (GSA)
- All branches: skin of face and meninges
- V1: opthalmic
- conjunctiva of eye
- bridge of nose
- nasal cavity
- V2: maxillary
- upper teeth, oral cavity
- nasal mucosa
- V3: mandibular
- lower teeth
- tongue
CN V: GSA location
- cell bodies of GSA neurons found in trigeminal ganglion
- located in middle cranial fossa
- inside cavernous sinus
CN V: Branchiomotor
- SVE
- CN V3 (mandibular n.)
- mm. of mastication: temporalis, messeter, medial and lateral pterygoids
- tensor veli palatini m.
- mylohyoid m.
- anterior belly of digastruc m.
- tensor tympani m.
Orbital Blowout Factures
- Fracture to the floor of the orbit
- maxilla and zygoma
- lateral walls sometimes involved
- Signs:
- Enopthalmos (sunken eye)
- restricted eye movements
- subconjunctival hemorrhage (from opthalmic a.)
- loss of sensation around orbit and zygoma (CN V2)
- Inferior rectus m. entrapment
- limited upward gaze in affected eye
- interior rectus m. herniates into maxillary sinus
- tension placed on eyeball limits motion of superior rectus m.
Trigeminal Neuralgia
- TNA, “typical TN”
- neuropathic pain in one side of the face
- may be in one or more trigeminal regions
- TNA caused by neurovascular compression of the trigeminal ganglion inside the cranial cavity
- compression-induces myelin loss causes pain
Trigeminal neuropathy
- TNO, “atypical TN”
- Peripheral damage due to trauma, usually to a single branch of CN V
- Myelin loss causes pain
- Axonal damage causes loss of sensation and/or motor function
Differential diagnoses of trigeminal neuropathies
TMJ disorders, dental infection