Lecture 2: Cranial Nerves Flashcards
What are the four parasympathetic ganglion?
Cilliary
Pterygopalatine
Otic
Submandibular
Mnemonic: Cats Prefer Smart Owners
Simply put, where are the 12 cranial nerves located?
Use Rule of 4s
Cranial Nerves 1-4 are above the pons
Cranial Nerves 5-8 in the pons
Cranial Nerves 9-12 in the medulla
Cranial Nerve I
What is this nerve?
What is it’s origin
Fun fact about nerve
Olfactory Nerve
Receptors in nasal mucosa of nasal cavity
Only type of nervous tissue to regenerate
What is CN I’s pathway
Travels through the foramina in cribiform plate of ethmoid bone and synapses in the olfactory bulb.
What is the modality & function of CN I?
How can CN I be damaged
What happens if this nerve is damaged?
Special Sensory: smell/olfaction
Fracture of cribiform plate
If damaged, can cause anosmia (partial or total loss of smell) or cerebrospinal fluid rhinorrhea
Cranial Nerve II
What is this nerve?
What is its origin?
Optic Nerve
Retina of the eye
What is the general tract (pathway) of CN II from the brain?
- Optic nerve fibers arise from ganglion cells in retina
- Enters cranium via optic foramen
- Nerves unite at optic chiasm
- Synapse onto lateral geniculate nucleus of thalamus
- Information is forwarded to the occipital lobe
What is the modality & function of CN II?
What happens if this nerve is damaged?
Special Sensory: vision
If damaged, can cause anopsia (visual defects) & loss of pupillary constriction
What cranial nerves go through the superior orbital fissure?
CN III - Occulomotor N.
CN IV - Trochlear N.
CN V1 - Opthalmic N.
CN VI - Abducens N.
Cranial Nerve III
What is this nerve?
What is it’s modality?
What is its origin?
Oculomotor Nerve
Somatic Motor (GSE) & Visceral Motor (GVE)
Oculumotor and Edinger Westphal nuclei within mesencephalon (midbrain)
What is the general tract of CN III from the brain?
- Leaves cranium via superior orbital fissure and travels to eye and eyelid.
- PS fibers travel to ciliary ganglion
- Post-gang PS fibers then travel to iris and ciliary muscle.
What is the parasympathetic motor function of CN III?
(What muscles is it innervating?)
Visceral Motor Functions
- Constricts the pupil: sphincter pupillae muscle (constrictor)
- Contracts cilliary muscle to make the lens of the eye more spherical and relaxed (as needed for near vision and to maintain focus)
Parasympathetic: Rest, Digest, READ
What is the somatic motor function of CN III?
Somatic Motor Functions
- Innervates intrinsic eye muscle: Elevates eyelid
- Levator Palpebrae Superioris Muscle
- Innervates extrinsic eye muscle: Move eyeball
- Superior Rectus Muscle
- Medial Rectus Muscle
- Inferior Rectus Muscle
- Inferior Oblique Muscle
What happens if CN III is damaged?
Oculomotor (CN III) Nerve Palsy
- Paralysis of eye muscles leading to strabismus
- eyes are not parallel and deviated improperly
- Ptosis (upper eleyid droop)
- Diplopia (double vision)
- Dilated pupil
- Difficulty with focusing
Gaze will be down and out!!
Cranial Nerve IV
What is this nerve?
What is it’s modality?
What is its origin?
Trochlear Nerve
Somatic Motor (GSE)
Trochlear nucleus within mesencephalon (midbrain)
What is the general tract of CN IV?
Leaves cranium via superior orbital fissue and travels to superior oblique muscle
What is the only nerve that exits on the dorsal surface of the brainstem?
Trochlear Nerve (CN IV)
What is the function of CN IV?
What happens if this nerve is damaged?
Somatic Motor: Innervates Superior Oblique Muscle (depresses, internally rotates, and abducts the eye)
Paralysis of superior oblique, leading to strabismus (cross eyes)
Inability to look down when eye is adducted
Diplopia (double vision)
Cranial Nerve VI
What is this nerve?
What is it’s modality?
What is its origin?
Abducens Nerve
Somatic motor (GSE)
Pontine (abducens) nucleus in pons
What is the general tract of CN VI?
Leaves cranium through superior oribital fissue and travels to lateral retus muscle
What is the function of CN VI?
What happens if this nerve is damaged?
Somatic Motor: Innervates Lateral Rectus Muscle (abducts eye)
ABDUCENT NERVE PALSY
- No lateral eye movement (can’t abduct eye)
- diplopia (double vision)
Cranial Nerve V
What is this nerve?
What is its CNS origin?
Trigeminal Nerve
Lateral side of Pons
Derivatives of 1st pharyngeal arch
What are the divisions of CN V?
CN V1: Ophthalmic Branch of the Trigeminal Nerve
CN V2: Maxillary Branch of the Trigeminal Nerve
CN V3: Mandibular Branch of the Trigeminal Nerve
What is the tract of the CN V1 division?
Sensory fibers enter cranium via superior orbital fissue and travel to trigeminal ganglion before entering pons
superior orbital fissue -> trigeminal ganglion -> pons
What is the function of CN V1?
Sensory Afferent
Conducts sensory impulses from cornea, nose, forehead and anterior scalp
What is the pathway for CN V2
foramen rotundum -> trigeminal ganglion -> pons
What is the function of CN V2?
Sensory Afferent
Skin of face, lower eyelid, nasal mucosa, upper lip, cheeks, maxillary teeth
What is the pathway for CN V3
Sensory:
foramen ovale -> trigeminal ganglion -> pons
Motor:
Pons -> foramen ovale -> muscles
What is the function of CN V3?
Sensory Afferent
- Sensory Impulses for Anterior 2/3 of the tongue (sense not taste)
- Skin of mandible (chin), lower jaw, lower teeth; one-third from sensory fibers of auricle of ear
Visceral Efferent (Branchial Motor)
- Innervates muscles of mastiation
- Innervates mylohyoid, anterior belly of digastric muscle, tensor tympani, and tensor veli palatini
CN V Damage
Loss of Pain & Touch sensations
paraesthesia
masseter and temporalis muscles do not contract
Deviation of mandible to side of lesion when mouth is open
Trigeminal Neuralgia (tic douloureux) produces exruciating, episodic pain that is usually restricted to the areas supplied by the maxillary and/or mandibular divisions of this nerve
Cranial Nerve VII
What is this nerve?
What is its origin?
Facial Nerve
Nuclei within the Pons
Derivatives of 2nd Pharyngeal Arch
What are the modalities of CN VII
- Branchial Motor (Special Visceral Efferent)
- Visceral Motor (General Visceral Efferent)
- General Sensory (General Somatic Afferent)
- Specail Sensory (Special Sensory Afferent)
What are the branches of CN VII and their function
Facial N. proper - Muscles of fascial expression, Posterior Belly of digastric M. & Stylohyoid M.
Chorda Tympani N. - Innervates submandibullar and sublingual salivary glands. Receives Special Sesonsory from anterior 2/3rds of tongue
Greater Petrosal N. - Innervates lacrimal, nasal & palatine glands
What is the pathway for CN VII Sensory Fibers
Travel from tongue via chorda tympani (branch of Facial N.) -> enter skull -> fibers synapse at geniculate ganglion of the Facial N.
CN VII Somatic Motor pathway
Leave the pons and enter the temporal through the internal acoustic meatus. Project through the temporal bone and emerge out the stylomastoid foramen to supply the musculature.
CN VII Parasympathetic motor pathway
PS motor fibers leave the pons, enter the internal aucoustic meatus, leave with either the greater petrosal nerve or chorda typani nerve, and travel to an autonomic ganglion before innervating their respective glands.
CN VII Branches to Muscles of Facial Expression
Posterior Aurcicular, Temporal, Zygomatic, Buccal, Mandibular & Cervical branch
A Tiny Zebra Bit My Cheek
Sensory Function of VII
Taste from anterior two-thirds of tongue
Somatic Motor Function of VII
The 5 major motor branches innervates the muscle of fascial expression, the posterior belly of the digastric muscle, and the stylohyoid and stapedius muscle.
What does the parasympathetic motor function of CN VII?
Greater Petrosal - Innervates Lacrimal, Palatine & Nasal glands
Chorda Tympani - Innervates Submandibular and Sublingual salivary glands
What CN is involved in closing the eye?
CN VII - Facial N. proper
What happens if CN VII is damged
Decreased tearing (dry eye)
Decreased salivation (dry mouth)
Loss of taste sensation to anterior 2/3 of tongue
Bell Palsy/Facial Nerve Palsy: Paralyzed facial muscle, eyelid droop, sagging at corner of mouth.
What CN is affected in Bell’s Palsy?
What occurs as a result?
CN VII
Inability to use facial muscles
Remembering CN VII functions
CN closes your eyes, tastes like pie (anteriror 2/3), makes you cry & innervates all the glands in the head except the one it goes through (parotid gland).
Cranial Nerve VIII
What is this nerve?
What is its modality?
What is its origin?
Vestibulocochlear Nerve
Special Sensory
Vestibular branch - Hair cells in the vestibule of inner ear
Cochlear branch - Cochlea of inner ear
What is the general tract of CN VIII?
Vestibular branch + cochlear branch meet then enter cranial cavity via the internal acoustic meatus and travel to junction of the pons and medulla oblongata (pontomedullary junction)
What is the function of CN VIII?
What happens if this nerve is damaged?
Hearing - cochlear branch
Balance - vestibular branch
If there is damage, can lead to loss balance, nausea, vomitting, dizziness, and deafness. Progressive unilateral hearing loss. Tinnutus (noises in ear)
Cranial Nerve IX
What is this nerve?
What is its CNS origin?
Glossopharyngeal Nerve
Medulla
Derivatives of 3rd pharyngeal arch
CN IX Modalities
Branchial Motor (SVE)
Visceral Motor (GVE)
Visceral Sensory (GVA)
General Sensory (GSA)
Special Sensory (SA)
What is the function of CN IX?
- General sensation and taste to posterior 1/3 of tongue
- chemoreceptor fibers to the carotid bodies (detect and monitor O2 & CO2 lvls in blood going to brain)
- Motor: Innervates stylopharyngeus (pharynx muscle)
- Para: Innervated parotid salivary gland
What is the Sensory Pathway of CN IX?
Sensory fibers travel from posterior 1/3 of tongue and carotid bodies along nerve through the inferior or superior ganglion into the jugular foramen and travel to pons
posterior 1/3 of tongue & carotid bodies –> inferior or superior ganglion –> jugular foramen –> pons
CN IX Motor Pathway
Somatic motor fibers leave the cranium via jugular foramen and travel to stylopharyngeaus M.
CN IX Parasympathetic Pathway
PS motor fibers travel to otic ganglion and then to parotid gland
What is the parasympathetic function of CN IX?
Innervates parotid salivary gland
CN IX Damage
Reduced salivary secretion (dry mouth), loss of taste sensations to posterior 1/3 of tongue; loss of sensation on affected side of soft palate.
Cranial Nerve X
What is this nerve?
What is its CNS origin?
Vagus Nerve
medulla oblongata
What are the modalities of CN X
Branchial Motor (SVE)
Visceral Motor (GVE)
Visceral Sensory (VA)
General Sensory (GSA)
What is the general tract of CN X?
Leaves cranium via jugular foramen before traveling and branching extensively in neck, thorax and abdomen; sensory neuron cell bodies are located in the superior and inferior gangla associates with the nerve.
What is the Sensory function of CN X?
Visceral sensory information from pharynx, larynx, heart, lungs and most abdominal organs.
General sensory information from external auditory canal, eardrum, and pharynx
Motor function of CN X
BM - Innervates palatoglossus (tongue M.) and most pharynx and larynx muscles
VM - Innervates smooth muscles and glands of heart, lungs, pharynx, larynx, trachea, and most abdominal organs
What is the parasympathetic function of CN X?
Innervates smooth muscles and glands of heart, lungs, larynx, trachea, and most abdominal organs
If CN X is damaged, what conditions can occur?
- Larnyx issues: hoarseness or loss of voice
- Difficulty Swallowing
- Impared gastrointestinal system mobility
- Deviation of Uvula away from the lesion
Which direction does the uvula deviate if there is a lesion on CN X?
Away from the side of the lesion
Cranial Nerve XI
What is this nerve?
What is its origin?
Spinal Accessory Nerve
cranial root - motor nuclei in medulla oblangata
spinal root - motor nuclei in spinal cord
What is the general tract of CN XI?
Spinal root travels superiorly to enter skull through foramen magnum. There the cranial and spinal roots merge and leave the skull via jugular foramen. Once outside the skull, cranial roots splits to travel with CN X (vagus) and spinal root travels to strenoclenoidmastoid and trapezius
What is the function of CN XI?
What happens if this nerve is damaged?
Special Visceral Efferent (Branchial Motor):
Cranial root - travels with CN X fibers to pharynx
Spinal root - supplies SCM and Trapezius muscles
If damaged, can lead to difficulty elevating shoulder (drooping of shoulders) or turning head to opposite side
Cranial Nerve XII
What is this nerve?
What is its origin?
Hypoglossal Nerve
hypoglossal nucleus in medulla oblongata
What is the general tract of CN XII?
Leaves cranium via hypoglossal canal; travels inferior to mandible and to inferior surface of tongue.
What is the function of CN XII?
What happens if this nerve is damaged?
Somatic Efferent: Supplies all intrinsic and extrensic muscles of the tongue except Palatoglossus Muscle (CN X).
If damaged, can lead to difficulty swallowing and speaking. If a single hypoglossal nerve is paralyzed, a protrude tongue deviates to the side of the damaged nerve.
Name means “under the tongue”
What direction will the tongue deviate if there is a lesion of the hypoglossal nerve on one side?
Towards the lesion
May atrophy
What nucleus do the parasympathetic fibers of CN VII travel with?
Superior salivatory nucleus
What nucleus do the parasympathetic fibers of CN IX arise from?
Inferior Salivatory nucleus
The ______ provides the efferent limb of the gag reflex while the ________ provodes the afferent limb of the gag reflex
- Vagus N. (CN X)
- Glossopharyngeal N (CN IX)
