Cranial Nerves and Autonomics Flashcards
What does the mnemonic Oh Oh Oh To Touch And Feel A Girls Vagina Ah Heavenly refer to?
(cranial nerves)
Olfactory (CN I)
Optic (CN II)
Oculomotor (CN III)
Trochlear (CN IV)
Trigeminal (CN V)
Abducens (CN VI)
Facial (CN VII)
Vestibulochochlear (CN VIII)
Glossopharyngeal (CN IX)
Vagus (CN X)
Accessory (CN XI)
Hypoglossal (CN XII)
What passes through the foramen cecum?
emissary vein to superior sagittal sinus
What passes through the nasal slit and anterior ethmoidal foramen?
anterior ethmoidal A., V., and N.
What passes through the foramina of cribriform plate?
olfactory nerve bundles
What passes through the posterior ethmoidal foramen?
posterior ethmoidal A., V., and N.
What passes through the optic canal?
optic N. (II) and ophthalmic A.
What passes through the superior orbital fissure?
oculomotor N. (III), trochlear N. (IV), lacrimal, frontal, and nasociliary branches of the ophthalmic N. (V1), abducent N. (VI), and superior ophthalmic V.
What passes through foramen rotundum?
maxillary nerve (V2)
What passes through the foramen ovale?
mandibular N. (V3), accessory meningeal A., lesser petrosal N. (occasionally)
What passes through the foramen spinosum?
middle meningeal A. and V., and meningeal branch of mandibular N.
What passes through the sphenoid emissary foramen (vesalius, inconstant)?
small emissary V.
What passes through the carotid canal?
internal carotid A. and internal carotid nerve plexus
What passes through the hiatus for lesser petrosal N. and hiatus for greater petrosal N.?
lesser petrosal N. and greater petrosal N. respectively
What passes through the internal acoustic meatus?
facial N. (VII), vestibulocochlear N. (VIII), and labyrinthe A.
What passes through the external opening of vestibular aqueduct?
endolymphatic duct
What passes through the mastoid foramen (inconstant)?
emissary V. (occasionally branch of occipital A.)
What passes through the jugular foramen?
inferior petrosal sinus, glossopharyngeal N. (IX), vagus N. (X), accessory N. (XI), sigmoid sinus, and posterior meningeal A.
What passes through the condylar canal (inconstant)?
emissary V. and meningeal branch of ascending pharyngeal A.
What passes through the hypoglossal canal?
hypoglossal N. (XII)
What passes through the foramen magnum?
medulla oblongata, meninges, vertebral As., meningeal branches of vertebra As., spinal roots of accessory Ns.
cranial nerve: olfactory
CN #:
foramen:
cranial nerve: olfactory
CN #: I
foramen: cribiriform plate
cranial nerve: optic
CN #:
foramen:
cranial nerve: optic
CN #: II
foramen: optic canal
cranial nerve: occulomotor
CN #:
foramen:
cranial nerve: occulomotor
CN #: III
foramen: superior orbital fissure
cranial nerve: trochlear
CN #:
foramen:
cranial nerve: trochlear
CN #: IV
foramen: superior orbital fissure
cranial nerve: opthalmic division of trigeminal
CN #:
foramen:
cranial nerve: opthalmic division of trigeminal
CN #: V (V1)
foramen: superior orbital fissure
cranial nerve: abducens
CN #:
foramen:
cranial nerve: abducens
CN #: VI
foramen: superior orbital fissure
cranial nerve: maxillary division of trigeminal
CN #:
foramen:
cranial nerve: maxillary division of trigeminal
CN #: V (V2)
foramen: foramen rotundum
cranial nerve: mandibular division of trigeminal
CN #:
foramen:
cranial nerve: mandibular division of trigeminal
CN #: V (V3)
foramen: foramen ovale
cranial nerve: facial
CN #:
foramen:
cranial nerve: facial
CN #: VII
foramen: internal acoustic meatus
cranial nerve: vestibulocochlear
CN #:
foramen:
cranial nerve: vestibulocochlear
CN #: VIII
foramen: internal acoustic meatus
cranial nerve: glossopharyngeal
CN #:
foramen:
cranial nerve: glossopharyngeal
CN #: IX
foramen: jugular foramen
cranial nerve: vagus
CN #:
foramen:
cranial nerve: vagus
CN #: X
foramen: jugular foramen
cranial nerve: accessory
CN #:
foramen:
cranial nerve: accessory
CN #: XI
foramen: jugular foramen
cranial nerve: hypoglossal
CN #:
foramen:
cranial nerve: hypoglossal
CN #: XII
foramen: hypoglossal canal
Modality: somatic motor, general somatic efferent
Name of Nucleus and Associated Nerves: oculomotor (III), trochlear (IV), abducens (VI), hypoglossal (XII)
Function:
Modality: somatic motor, general somatic efferent
Functions:
oculomotor (III): all extraocular eye muscles except superior, oblique, and lateral rectus
trochlear (IV): superior oblique
abducens (VI): lateral rectus
hypoglossal (XII): intrinsic and extrinsic tongue muscles except palatoglossus
Modality: brachial motor, special visceral efferent
Name of Nucleus and Associated Nerves: masticator (V), facial (VII), ambiguus (IX, X), accessory (XI)
Function:
Modality: brachial motor, special visceral efferent
Functions:
masticator (V): muscles of mastication
facial (VII): muscles of facial expression
ambiguus (IX, X): muscles of pharynx and larynx
accessory (XI): trapezius and sternomastoid
Modality: visceral motor (parasympathetic), general visceral efferent
Name of Nucleus and Associated Nerves: Edinger-Westphal (III), superior salivatory (VII), inferior salivarory (IX), dorsal vagus (X)
Function:
Modality: visceral motor (parasympathetic), general visceral efferent
Functions:
Edinger-Westphal (III): ciliary muscle and constrictor pupillae
superior salivatory (VII): all glands of the head except integumentary and parotid
inferior salivarory (IX): parotid gland
dorsal vagus (X): all thoracic viscera and abdominal viscera to the splenic flexure
Modality: visceral sensory, general visceral afferent
Name of Nucleus and Associated Nerves: solitarius (IX, X)
Function:
Modality: visceral sensory, general visceral afferent
Functions:
solitarius (IX, X): visceral afferent information necessary for visceral reflexes, nausea, but not pain
Modality: general sensory, general sensory afferent
Name of Nucleus and Associated Nerves: trigeminal (V, VII, IX, X)
Function:
Modality: general sensory, general sensory afferent
Functions: trigeminal (V, VII, IX, X): pain, temperature, touch, proprioception from the head and neck, sinuses, and meninges
Modality: special sensory, special sensory afferent
Name of Nucleus and Associated Nerves: mitral cells of olfactory bulb (I), ganglion cells of retina (II), gustatory (VII, IX), vestibular (VIII), cochlear (VIII)
Function:
Modality: special sensory, special sensory afferent
Functions:
mitral cells of olfactory bulb (I): smell
ganglion cells of retina (II): vision
gustatory (VII, IX): taste
vestibular (VIII): balance
cochlear (VIII): hearing
Arch: first (mandibular)
Nerve: trigeminal (CN V) (ophthalmic division does not supply any pharyngeal arch components)
Muscles:
Skeletal structures:
Ligaments:
Arch: first (mandibular)
Nerve: trigeminal (CN V)
Muscles: muscles of mastication (temporalis, massecter, medial, and lateral pterygoids), mylohyoid and anterior belly of digastric, tensor tympanic, and tensor veli palatini
Skeletal structures: malleus and incus
Ligaments: anterior ligaments of malleus, sphenomandibular ligament
Arch: second (hyoid)
Nerve: facial (CN VII)
Muscles:
Skeletal structures:
Ligaments:
Arch: second (hyoid)
Nerve: facial (CN VII)
Muscles: muscles of facial expression (buccinator, auricularis, frontalis, platysma, orbicularis oris, and oculi), stapedius, and stylohyoid
Skeletal structures: stapes, styloid process, lesser cornu of hyoid, and upper part of body of hyoid bone
Ligaments: stylohyoid ligament
Arch: third
Nerve: glossopharyngeal (CN IX)
Muscles:
Skeletal structures:
Arch: third
Nerve: glossopharyngeal (CN IX)
Muscles: stylopharyngeus
Skeletal structures: greater cornu of hyoid, lower part of body of hyoid bone
Arch: fourth and sixth (fifth is often absent, cartilaginous components of fourth and sixth fuse to form cartilages of the larynx)
Nerve: superior laryngeal branch of vagus (CN X), recurrent laryngeal branch of vagus (CN X)
Muscles:
Skeletal structures:
Arch: fourth and sixth
Nerve: superior laryngeal branch of vagus (CN X), recurrent laryngeal branch of vagus (CN X)
Muscles: cricothyroid, levator veli palatini, constrictors of pharynx, intrinsic muscles of larynx, and striated muscles of esophagus
Skeletal structures: thyroid cartilage, cricoid cartilage, arytenoid cartilage, corniculate cartilage, cuneiform cartilage
General Rules of Autonomics in the Head
- all sympathetic fibers are postganglionic arising from the superior cervical ganglion of the sympathetic trunk; they travel on vessels to the structures that they innervate (____ ______ _____)
- preganglionic parasympathetic fibers arise from nuclei in the brain stem and synapse at 4 ganglia in the head:
- preganglionic parasympathetics are carried by cranial nerves:
- all postganglionic fibers “piggy back” on a branch of the _______ to arrive at the structure that they innervate
General Rules of Autonomics in the Head
- all sympathetic fibers are postganglionic arising from the superior cervical ganglion of the sympathetic trunk; they travel on vessels to the structures that they innervate (deep petrosal nerve)
- preganglionic parasympathetic fibers arise from nuclei in the brain stem and synapse at 4 ganglia in the head: cilliary, pterygopalatine, otic, and submandibular
- preganglionic parasympathetics are carried by cranial nerves: oculomotor (III), facial (VII), glossopharyngeal (IX), and vagus (X)
- all postganglionic fibers “piggy back” on a branch of the trigeminal to arrive at the structure that they innervate
olfactory N. (CN I)
description:
sensory function:
origin:
pathway:
conditions caused by nerve damage:
olfactory N. (CN I)
description: conducts olfactory (smell) sensations to brain; only type of nervous tissue to regenerate
sensory function: olfaction (smell)
origin: receptors (bipolar neurons) in olfactory mucosa of nasal cavity
pathway: travels through the foramina in cribriform plate of ethmoid bone and synapses in the olfactory bulbs, located in the anterior cranial fossa
conditions caused by nerve damage: anosmia (partial or total loss of smell)
optic N. (CN II)
description:
sensory function:
origin:
pathway:
conditions caused by nerve damage:
optic N. (CN II)
description: special sensory nerve of vision that is an outgrowth of the brain; more appropriately called a brain tract
sensory function: vision
origin: retina of the eye
pathway: enters cranium via optic foramen of sphenoid bone; left and right optic nerves unite at the optic chiasm; optic tracts travel to lateral geniculate nucleus of thalamus; finally, info is forwarded to the occipital lobe
conditions caused by nerve damage: anopsia (visual defects)
What would damage in area 1 lead to?
total blindness of right eye due to complete lesion of right optic nerve
What would damage in area 2 lead to?
right nasal hemianopia due to lesion involving right perichiasmal area
What would damage in area 3 lead to?
bipolar hemianopia due to midline chiasmal lesion
What would damage in area 4 lead to?
left homonymous hemianopia due to lesion or pressure on right optic tract
What would damage in area 5 lead to?
left homonymous inferior quadrantanopia due to involvement of lower right optic radiations
What would damage in area 6 lead to?
left homonymous superior quadrantanopia due to involvement of upper right optic radiations
What would damage in area 7 lead to?
left homonymous hemianopia due to lesion of right occipital lobe
oculomotor N. (CN III)
description:
somatic motor function:
parasympathetic motor function:
origin:
pathway:
conditions caused by nerve damage:
oculomotor N. (CN III)
description: innervates upper eyelid muscle and four of the six extrinsic eye muscles; name means “eye” and “moving”
somatic motor function: supplies four extrinsic eye muscles (superior/inferior/medial rectus and inferior oblique) that move eyeball; supplies levator palpebrae superioris muscle to elevate eyelid
parasympathetic motor function: innervates sphincter pupillae muscle of iris to make pupil constrict; contracts ciliary muscles to make the lens of eye more spherical (as needed for near vision)
origin: oculomotor and Edinger-Westphal nuclei within mesencephalon
pathway: leaves cranium via superior orbital fissure and travels to eye and eyelid (parasympathetic fibers travel to ciliary ganglion, and postganglionic parasympathetic fibers then travel to iris and ciliary muscles)
conditions caused by nerve damage: ptosis (upper eyelid droop), paralysis of eye muscles, leading to strabismus (eyes not in parallel/deviated improperly), diplopia (double vision), and difficulty focusing
- in the absence of nerve stimulation (no parasympathetic stimulation), the ciliary muscle is ______
- lens is thus ________ _____ to refract light for _______ vision
- _______ fibers are under tension
- in the absence of nerve stimulation (no parasympathetic stimulation), the ciliary muscle is relaxed
- lens is thus stretched thin to refract light for distant vision
- Zonular fibers are under tension
trochlear N. (CN IV)
description:
somatic motor function:
origin:
pathway:
conditions caused by nerve damage:
trochlear N. (CN IV)
description: name means “pulley,” because it innervates one extrinsic eye muscle (superior oblique) that loops through a pulley-shaped ligament
somatic motor function: supplies superior oblique to move eyeball inferiorly and laterally
origin: trochlear nucleus within mesencephalon
pathway: leaves cranium via superior orbital fissure and travels to superior oblique muscle
conditions caused by nerve damage: paralysis of superior oblique, leads to strabismus (eyes not in parallel/deviated improperly) and diplopia
abducens N. (CN VI)
description:
somatic motor function:
origin:
pathway:
conditions caused by nerve damage:
abducens N. (CN VI)
description: innervates lateral rectus eye muscle (aducts eye) = “pulls away laterally”
somatic motor function: innervates lateral rectus for eye abduction
origin: pontine (abducens) nucleus in pons
pathway: leaves cranium through superior orbital fissure and travels to lateral rectus muscle
conditions caused by nerve damage: paralysis of lateral rectus limits lateral movement of eye; diplopia
eye movements by muscles and innervation
- upward to the side:
- directly upward:
- directly to the side:
- downward to the side:
- directly downward:
eye movements by muscles and innervation
- upward to the side: inferior and superior rectus Ms., oculomotor N. (CN III)
- directly upward: superior rectus and inferior oblique Ms., oculomotor N. (CN III)
- directly to the side: “outside” eye: lateral rectus M., abducent N. (CN VI); “inside” eye: medial rectus M., oculomotor N. (CN III)
- downward to the side: “outside” eye: superior oblique M., trochlear N. (CN IV); “inside” eye: inferior rectus M., oculomotor N. (CN III)
- directly downward: inferior rectus M. (oculomotor N., CN III) and superior oblique M. (trochlear N., CN IV)
- condition that causes right eye to have a downward and outward gaze and dilated pupil; eyelid must be elevated manually due to ptosis
- left eye is normal
right oculomotor (CN III) nerve palsy
- condition that hinders left eye from abducting
- right eye is normal
left abducent (CN VI) nerve palsy
trigeminal N. (CN V)
description:
sensory function:
branchial motor function:
origin:
pathway:
conditions caused by nerve damage:
trigeminal N. (CN V)
description: 3 divisions, ophthalmic (V1), maxillary (V2), and mandibular (V3); receives sensory info from face, oral cavity, nasal cavity, anterior scalp, and innervates muscles of mastication
sensory function: V1 (conducts sensory impulses from cornea, nose, forehead, anterior scalp), V2 (conducts sensory impulses from nasal mucosa, palate, gums, cheek), V3 (conducts sensory impulses from anterior 2/3rds of tongue, skin of chin, lower jaw, lower teeth; 1/3rd from sensory fibers of auricle of ear)
branchial motor function: innervates muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani muscle, and tensor veli palatini
origin: pons
pathway: V1 (sensory fibers enter cranium via orbital fissure and travel to trigeminal ganglion, before entering pons), V2 (sensory fibers enter cranium via foramen rotundum and travel to trigeminal ganglion, before entering pons), V3 (motor fibers leave pons and exit cranium via foramen ovale to supply muscles, sensory fibers travel through foramen ovale to trigeminal ganglion, before entering pons)
conditions caused by nerve damage: trigeminal neuralgia (tic douloureux) caused by inflammation of sensory components of trigeminal nerve and results in intense, pulsating pain lasting from minutes to several hours
What are the branches off the ophthalmic (V1) division of trigeminal N. (CN V)?
- lacrimal N.
- frontal N.: supratrochlear and supraorbital N. from frontal air sinus
- nasociliary: long ciliary Ns., posterior ethmoidal N., infratrochlear N., anterior ethmoidal N. (gives rise to eternal nasal N.)
- meningeal branch (from the tentorium cerebelli)
What are the branches of the maxillary (V2) division of the trigeminal N. (CN V)?
Meningeal nerve,
Ganglionic branches,
Zygomatic nerve
Posterior superior alveolar nerve
Infraorbital nerve
Orbital branches
Nasopalatine nerve
Posterior superior nasal nerves (lateral and medial)
Palatine nerves (greater and lesser)
Pharyngeal nerve
What are the branches off the mandibular (V3) division of the trigeminal N. (CN V)?
- sensory motor
- buccal
- lingual
- inferior alveolar: dental, incisive, mental
- auriculotemporal: anterior auricular, external acoustic meatus, temporomandibular joint, superficial temporal
- branchial motor
- medial pterygoid: tensor veli palatini and tensor tympani
- lateral pterygoid
- masseteric
- deep temporal
- mylohyoid: nerve to mylohyoid and nerve to anterior belly of digastric
*image can be used for all the branches of the trigeminal N. divisions*
facial N. (CN VIII)
description:
sensory function:
somatic motor function:
parasympathetic motor function:
origin:
pathway:
conditions caused by nerve damage:
facial N. (CN VIII)
description: innervates muscles of facial expression, lacrimal (tear) gland, and most salivary glands; conducts sensations from the anterior 2/3rds of the tongue
sensory function: taste from anterior 2/3rds of the tongue
somatic motor function: 5 major branches (temporal, zygomatic, buccal, mandibular, and cervical) innervate the muscles of facial expression, the posterior belly of the digastric muscle, and the stylohyoid and stapedius muscles
parasympathetic motor function: innervates (increases secretions of) the lacrimal gland of the eye and two salivary glands: the submandibular and sublingual glands
origin: nuclei within the pons
pathway: sensory fibers travel from tongue (via chorda tympani) branch of facial N., through tiny foramen to enter skull, fibers synapse at geniculate ganglion of facial N. Somatic fibers leave pons and enter temporal bone through internal auditory canal, project through temporal bone, and emerge through stylomastoid foramen to supply musculature. Parasympathetic motor fibers leave pons, enter internal auditory canal, leave w/ either greater petrosal N. or chorda tympani N., and travel to an autonomic ganglion before innervating respective glands
conditions caused by nerve damage: decreased tearing and salivation, loss of taste sensation to anterior 2/3rds of tongue and/or facial nerve palsy (Bell palsy) characterized by paralyzed facial muscles, eyelid droop, and sagging at corner of mouth
What is the pathway of the visceral (parasympathetic) motor fibers to lacrimal gland?
- greater petrosal N. arises from CN VII at geniculate ganglion and emerges from superior surface of petrous part of temporal bone to enter middle cranial fossa
- greater petrosal N. joins deep petrosal N. (sympathetic) at foramen lacerum to form nerve of pterygoid canal
- nerve of pterygoid canal travels through pterygoid canal and enters pterygopalatine fossa
- parasympathetic fibers from nerve of pterygoid canal in pterygopalatine fossa synapse in pterygopalatine ganglin
- postsynaptic parasympathetic fibers from this ganglion innervate lacrimal gland via zygomatic branch of CN V2 and lacrimal nerve (branch of CN V1)
What is the pathway of the visceral (parasympathetic) motor fibers to submandibular and sublingual glands?
- chorda tympani branch arises from CN VII just superior to stylomastoid foramen
- chorda tympani crosses tympanic cavity medial to handle of malleus
- chorda tympani passes through petrotympanic and petrous parts of temporal bone to join the lingual N. (CN V3) in infratemporal fossa
- parasympathetic fibers of chorda tympani synapse in submandibular ganglion; postsynaptic fibers follow arteries to glands
vestibulocochlear N. (CN VIII)
description:
sensory function:
origin:
pathway:
conditions caused by nerve damage:
vestibulocochlear N. (CN VIII)
description: conducts equilibrium and auditory sensations to brain; formerly called the auditory nerve or acoustic nerve
sensory function: cochlear branch conducts impulses for hearing, while vestibular branch conducts impulses for equlibrium
origin: vestibular branch (hair cells in the vestibule of the inner ear), cochlear branch (cochlea of the inner ear)
pathway: sensory cell bodies of vestibular branch are located in the vestibular ganglion, while sensory cell bodies of the cochlear branch are located in the spiral ganglion near the cochlea; the vestibular and cochlear branches merge, and together enter cranial cavity through internal auditory canal and travel to junction of the pons and the medulla oblongata
conditions caused by nerve damage: lesions in vestibular branch produce loss of balance, nausea, vomiting, and dizziness; lesions in cochlear branch result in deafness
glossopharyngeal N. (CN IX)
description:
sensory function:
somatic motor function:
parasympathetic motor function:
origin:
pathway:
conditions caused by nerve damage:
glossopharyngeal N. (CN IX)
description: receives taste and touch sensations from posterior tongue structures, one pharynx muscle, and parotid salivary gland
sensory function: general sensation and taste to the posterior 1/3 of tongue; chemoreceptor fibers to the carotid bodies (structures on the carotid arteries that detect and monitor O2 and CO2 levels in the blood)
somatic motor function: innervates stylopharyngeus (pharynx muscle)
parasympathetic motor function: innervates (thus increasing secretion of) parotid salivary gland
origin: sensory fibers originate on taste buds and mucosa of posterior 1/3 of the tongue, as well as the carotid bodies; motor fibers originate in nuclei in the medulla oblongata
pathway: 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; somatic motor fibers leave cranium via jugular foramen and travel to stylopharyngeus, while sensory fibers go to posterior 1/3 of tongue and carotid bodies; parasympathetic motor fibers travel to otic ganglion and then to parotid gland
conditions caused by nerve damage: reduced salivary secretion, loss of taste sensations to posterior 1/3 of tongue
What is the pathway of visceral (parasympathetic) motor fibers to the parotid gland?
- tympanic N. arises from CN IX and emerges w/ it from jugular foramen
1. tympanic N. enters middle ear via tympanic canaliculus in petrous part of temporal bone
2. tympanic N. forms tympanic plexus on promontory of middle ear
3. lesser petrosal N. arises as a branch of tympanic plexus
3. lesser petrosal N. penetrates roof of tympanic cavity (tegmen tympani) to enter middle cranial fossa
4. lesser petrosal N. leaves cranium through foramen ovale
5. parasympathetic fibers synapse in otic ganglion
6. postsynaptic fibers pass to parotid gland via branches of auriculotemporal N. (CN V3)
vagus N. (CN X)
description:
sensory function:
somatic motor function:
parasympathetic motor function:
origin:
pathway:
conditions caused by nerve damage:
vagus N. (CN X)
description: innervates structures in the head and neck and in the thoracic and abdominal cavities
sensory function: visceral sensory info from pharynx, larynx, heart, lungs, and most abdominal organs; general sensory info from external auditory canal, eardrum, and pharynx
somatic motor function: innervates most pharynx muscles and larynx muscles
parasympathetic motor function: innervates visceral smooth muscle, cardiac muscle, and glands of heart, lungs, pharynx, larynx, trachea, and most abdominal organs
origin: motor nuclei in medulla oblongata
pathway: leaves cranium via jugular foramen before traveling and branching extensively in neck, thorax, and abdomen; sensory neuron cell bodies are located in superior and inferior ganglia associated w/ the nerve
conditions caused by nerve damage: paralysis leads to variety of larynx problems, including hoarseness, monotone, or complete loss of voice; other lesions may cause difficulty swallowing or impaired GI system mobility
accessory N. (CN XI)
description:
somatic motor function:
origin:
pathway:
conditions caused by nerve damage:
accessory N. (CN XI)
description: innervates trapezius, sternocleidomastoid, and some pharynx muscles; formerly called “spinal accessory N.”
somatic motor function: cranial root (travels w/ CN X fibers to pharynx), spinal root (innervates trapezius and sternocleidomastoid)
origin: cranial root (motor nuclei in medulla oblongata), spinal root (motor nuclei in spinal cord)
pathway: spinal root travels superiorly to enter skull through foramen magnum; there, cranial and spinal roots merge and leave the skull via jugular foramen; once outside skull, cranial root splits to travel w/ CN X, and spinal root travels to sternocleidomastoid and trapezius
conditions caused by nerve damage: paralysis of trapezius and sternocleidomastoid, results in difficulty elevating shoulder or turning head to opposite side
hypoglossal N. (CN XII)
description:
somatic motor function:
origin:
pathway:
conditions caused by nerve damage:
hypoglossal N. (CN XII)
description: innervates intrinsic and extrinsic tongue muscles; name means “under the tongue”
somatic motor function: innervates intrinsic tongue muscles (e.g. muscle fibers of tongue itself) and extrinsic tongue muscles (e.g. hypoglossus, genioglossus, styloglossus)
origin: hypoglossal nucleus in medulla oblongata
pathway: leaves cranium via hypoglossal canal; travels inferior to mandible and to inferior surface of tongue
conditions caused by nerve damage: swallowing and speech difficulties due to impaired tongue movement; if single hypoglossal N. (left or right) is paralyzed, a protruded tongue deviates to the side of damaged nerve
What occurs with a unilateral (one-sided) CN XII lesion?
tongue atrophies or turns toward lesioned side when protruded
