M2 Study Guide Flashcards
afferent
to CNS
sensory
efferent
away from CNS
motor
what does the proencephalon (forebrain) consist of
telencephalon (cerebrum)
- olfactory (CN I): sensory only
what does the diencephalon (deep brain and hypothalamus, thalamus, and epithalamus) consist of
optic (CN II): sensory only
what does the rhombencephalon (hindbrain) consist of
metencephalon (pons)
myelencephalon (medulla)
what does the mesencephalon (midbrain) consist of
oculomotor (CN III): motor only
trochlear (IV): motor only
what does the myelencephalon (medulla) consist of
vestibulocochlear (VIII): sensory.
glossopharyngeal (IX): mixed.
vagus (X): mixed.
spinal accessory (XI): motor.
hypoglossal (XII): motor.
what does the metencephalon consist of
Trigeminal (V): mixed.
- ophthalmic (V1): sensory
- maxillary (V2): sensory
- mandibular (V3): mixed
abducens (VI): motor
facial (VII): mixed
what is the midbrain
connector between forebrain and hindbrain
what type of fibers does CN I have
sensory only (SVA)
sensory ganglia of the head
trigeminal (V)
geniculate (VII)
are autonomic ganglia of the head sympathetic or parasympathetic
parasympathetic because the ganglion for sympathetic innervation to the head and neck is located in the thorax as the superior-most ganglion of the sympathetic trunk = superior cervical ganglion
what are the autonomic ganglia of the head and what do they innervate
Ciliary (CN III):
- pupil constriction (miosis)
- accommodation (increased focusing ability of eye).
Pterygopalatine (VII):
- lacrimal and glands in nasal cavity and maxillary sinus (increased secretion).
Submandibular (VII):
- submandibular and sublingual salivary glands (increased secretion).
Otic (IX):
- parotid salivary gland (increased secretion).
what can happen to CN I following trauma
can be sheared by olfactory foramen.
ex. acceleration-deceleration such as automobile collisions
location of olfactory bulb
rests on cribriform plate of ethmoid within anterior cranial fossa
where do CN I rootlets enter
anterior cranial fossa via olfactory foramina within cribriform plate of ethmoid
where do the olfactory tracts from bulb project
telencephalon
ex. cerebrum
what fibers is CN II
sensory only (SA)
what is the optic nerve comprised of
retinal ganglion cells (RGCs) surrounded by meninges, so there are some CNS characteristics
where does the optic nerve exit orbit
via optic canal in the middle cranial fossa above cavernous sinus
where does the optic nerve go after passing through the optic chiasm
project to lateral geniculate bodies (as optic tract), which are located within thalamus of diencephalon
what fibers are CN III (oculomotor nerve)
motor only.
GSE.
GVE
what is innervated by CN III
extraocular muscles:
- superior rectus
- inferior rectus
- medial rectus
- inferior oblique
where does CN III carry autonomic input to
carries GVE to iris sphincter muscle for pupil constriction and ciliary muscle for accommodation via ciliary ganglion (autonomic ganglion for CN III)
explain the “down and out” eye appearance in complete oculomotor palsy
superior oblique and lateral rectus are not affected because they are innervated by trochlear and abducens nerves, so the opposing muscles pull the eye “down” and “out”.
pupils may be affected: mydriasis - dilated pupil - as result of loss of pupillary constrictor muscle function as parasympathetic preganglionic fibers ‘ride’ along outside oculomotor nerve.
aneurysms of internal carotid artery in cavernous sinus typically associated with oculomotor palsies.
what does CN III emerge from and pass through
emerges from midbrain (mesencephalon), passes through cavernous sinus within middle cranial fossa and into orbit via superior orbital fissure (SOF).
what fiber is CN IV (trochlear nerve)
motor only.
GSE
what does CN IV innervate
extraocular muscle: superior oblique
pathway of CN IV
emerges from midbrain, passes through cavernous sinus and exits middle cranial fossa into orbit via SOF
what fibers are CN V (trigeminal nerve)
mixed.
GSA
SVE
what occurs secondary to reactivation of herpes zoster virus
herpes zoster ophthalmicus
hutchinson’s sign
vesicles at tip of nose, which is innervated by a branch of V1
assessing CN V clinically
CN V1: supraorbital nerve –> brach of frontal nerve of V1.
CN V2: infraorbital nerve.
CN V3: mental nerve –> branch of inferior alveolar nerve of V3.
main branches of the sensory division (GSA) of CN V V1
lacrimal
frontal
nasociliary
sensory innervation the sensory division of of CN V V1
eye and orbit
facial skin above orbits
midline region of nose to tip
pathway of CN V V2
enters middle cranial fossa from pterygopalatine fossa via foramen rotundum then passes through cavernous sinus to the pons
main branches of CN V V2
zygomatic (lateral wall of orbit) and infraorbital (runs from surface of cheek through maxilla and enters floor of orbit) pass through inferior orbital fissure into pterygopalatine fossa where it becomes maxillary
sensory innervation of CN V V2
facial skin below orbits and above mouth and lateral to orbit.
maxillary sinus - located within maxilla
what type of nerve is CN V V3
mixed nerve
motor innervation of CN V V3
major muscles of mastication (SVE):
- masseter
- temporalis
- medial pterygoid
- lateral pterygoid
sensory innervation of CN V V3
area from below mouth arcing lateral and upward to just anterior of external ear.
nasal cavity.
anterior 2/3s of tongue (lingual nerve).
all are GSE
lingual nerve
runs next to autonomic fibers from chorda tympani to the submandibular ganglion
what is the mental nerve a branch of
inferior alveolar nerve
what is the inferior alveolar nerve typically evaluated for
CN V V3 integrity during cranial nerve testing
what does CN V V3 exit/enter and pass through
exits/enters middle cranial fossa via foramen ovale but does NOT pass through cavernous sinus because ovale is in the FLOOR of middle cranial fossa BELOW cavernous sinus
what fibers is CN VI (abducens)
motor only.
GSE
what muscle is innervated by CN VI (abducens)
extraocular muscle: lateral rectus
what does CN VI palsy result in
loss of abduction - eye cannot turn outward
what does CN VI emerge from and pass through
emerges from pons.
passes through cavernous sinus and into the orbit via superior orbital fissure
what does CN VI pass over after emerging from the CNS and into the middle cranial fossa
passes over sharp-edged petrous portion of the temporal bone which makes this CN more susceptible to injury/damage from a head injury, or certain medical conditions like diabetes
what nerve fibers make up CN VII (facial)
mixed nerve.
GSA
SVA
GVE
SVE
where do CN VII nuclei lie
within the pons near those for CN VI
where does CN VII enter/exit
exits/enters posterior cranial fossa via internal acoustic (auditory) meatus and eventually exits skull at stylomastoid foramen (between styloid and mastoid processes of temporal bone)
what root does CN VII contain
large motor and smaller intermediate (sensory and autonomic) root
major motor root branches of CN VII and what they control
Stapedial: controls amplitude of sound waves to inner ear by preventing excess movement of one of the ear ossicles (stapes).
Posterior auricular: motor to occipital muscle on back of head.
Two motor branches to stylohyoid and posterior belly of digastric muscles (aids in swallowing).
Terminal branches: 5 motor branches to muscles of facial expression - from superior to inferior:
- temporal
- sygomatic
- buccal
- mandibular
- cervical
major intermediate (sensory and autonomic) root branches of CN VII
Chorda tympani (GVE and SVA fibers).
Greater petrosal nerve (GVE)
GVE innervation of chorda tympani
autonomic innervation to submandibular and sublingual glands via submandibular ganglion and alongside lingual nerve, a sensory branch of CN V V3
SVA innervation of chorda tympani
sensory innervation for taste from anterior 2/3rds of tongue.
first run alongside lingual nerve before chorda tympani
what axons does the greater petrosal nerve contain and where do they originate
contains preganglionic parasympathetic axons.
originates at geniculate ganglion and passes into the middle cranial fossa –> joins with deep petrosal nerve
what axons does the deep petrosal nerve contain and where do they come from and go
postganglionic sympathetic axons that come from superior cervical ganglion in the neck.
enter middle cranial fossa via foramen lacerum and join up immediately with the internal carotid that passes into the cranium via carotid canal immediately adjacent to lacerum
what does the deep petrosal nerve become
nerve of pterygoid canal
what happens within the pterygopalatine ganglion within the fossa
preganglionic parasympathetic fibers synapse with postganglionic fibers in pterygopalatine ganglion while postganglionic sympathetic fibers pass directly through with both innervating nasal glands and lacrimal gland
old pathway to lacrimal gland from pterygopalatine ganglion
maxillary (CN V V2) –> zygomatic branch of maxillary –> lacrimal nerve (branch of CN V V1) –> lacrimal gland
new pathway to lacrimal gland from pterygopalatine ganglion
direct innervation to lacrimal gland via nerve plaxus from pterygopalatine ganglion
what fibers are CN VIII (vestibulocochlear)
sensory only.
SSA
where does CN VIII enter
enters posterior cranial fossa (along with CN VII) via internal acoustic (auditory) meatus to medulla of hindbrain
how many sensory ganglia does CN VIII have
2 - each associated with balance and hearing
what are the 2 divisions of CN VIII
vestibular (balance) and cochlear (hearing)
what nerve fibers are in CN IX (glossopharyngeal)
mixed nerve.
GSA
GVA
SVA
GVE
SVE
where are CN IX nuclei located and where does it exit/enter
nuclei located within medulla.
exits/enters posterior cranial fossa via jugular foramen.
CN IX sensory innervation
GSA: touch to posterior 1/3rd of tongue, tympanic cavity, auditory tube (Eustachian or pharyngotympanic tube), oropharynx (back of oral cavity/mouth).
SVA: taste posterior 1/3rd of tongue.
GVA: chemoreceptors and baroreceptors in carotid aa.
CN IX motor innervation
SVE: skeletal muscle innervation to muscles of pharynx (aid in swallowing).
GVE: autonomic innervation to parotid gland via otic ganglion
what is the tympanic nerve a major branch of and what does it innervate
major branch of CN IX.
innervates tympanic plexus.
what does the lesser petrosal nerve innervate from
innervates from tympanic plexus and carries preganglionic parasympathetic the final way to the otic ganglion where it synapses with postganglionic parasympathetic fibers
where is the otic ganglion located
outside the skull and adjacent to foramen ovale
what do the postganglionic parasympathetic fibers from the otic ganglion ‘hop’ on to
outside of the auriculotemporal nerve and travel to innervate parotid gland nearby
what is the auriculotemporal nerve
sensory branch of CN V V3 as it conveys information from sensory receptors in the skin proximal to parotid gland to CNS
where are the parotid located
immediately anterior to external ear
what nerve fibers make up CN X (vagus)
mixed nerve.
GSA
GVA
SVA
GVE
SVE
where are CN X nuclei located and where do they exit/enter
within medulla.
exits/enters posterior cranial fossa via jugular foramen
where does CN X run
inferiorly within the carotid sheath - between internal carotid/common carotid aa. and internal jugular v. to supply neck, thorax, and abdominal structures (most extensive distribution of all CNs
CN X sensory innervation
GSA:
- external auditory ear canal/small portion of ear lobe
- middle ear
- larynx/laryngopharynx
- dura mater in posterior cranial fossa
SVA:
- taste from pharynx and epiglottis
GVA:
- aortic body/arch and esophagus
- heart
- lungs
- abdominal organs and viscera
CN X motor innervation
SVE:
- skeletal muscles of the soft palate, larynx/pharynx, and one muscle of the tongue
GVE:
- smooth muscle innervation to pharynx/larynx, thorax, and abdominal organs/viscera
what nerve fibers are CN XI (spinal accessory)
motor only
SVE - possibly originates from 6th branchial arch for cranial root.
GSE - spinal root
where are CN XI nuclei located
within medulla
where does the CN XI cranial root exit
exits skull along with spinal root via jugular foramen and travels with CN X
