Intro to Cranial Nerves Flashcards
What are the functional modalities of cranial neurons?
general somatic afferent (GSA), general somatic efferent (GSE), general visceral afferent (GVA), general visceral efferent (parasympathetics, GVE),special sense (SVE) such as olfaction, taste, hearing, and balance
What is derived from pharyngeal arches?
branchiomeric mm.
What is associated with pharyngeal arch 1?
Cranial nerve 5, trigeminal nerve
branchiomeric muscles- mm. mastication, tensor tympani, tensor veli palantini, mylohyoid, ant. belly digastric
skeletal derivatives- malleus, incus, sphenomandibular lig.
What is associated with pharyngeal arch 2?
Cranial nerve VII, facial nerve
branchiomeric mm.- mm. facial expression, stapedius, stylohyiod, posterior belly digastric
skeletal derivatives- stapes, styloid process, stylohyiod ligament, lesser horn and superior body of hyoid
What is associated with pharyngeal arch 3?
Cranial nerve IX, glossopharyngeal n.
branchiomeric mm- stylopharyngeus
skeletal derivatives- greater horn and inferior body of hyoid
What is associated with pharyngeal arch 4 and 6?
Cranial nerve X, vagus nerve
branchiomeric mm.- most palatal mm., most pharyngeal mm., all laryngeal mm.
skeletal derivatives- laryngeal cartilages
CN I
olfactory nerve
CN II
optic nerve
CN III
Oculomotor nerve
CN IV
trochlear nerve
CN V
trigeminal
V1- ophthalmic
V2- maxillary
V3- mandibular
CN VI
Abducens n.
CN VII
facial nerve
CN VIII
Vestibulocochlear nerve
CN IX
glossopharyngeal nerve
CN X
vagus nerve
CN XI
accessory nerve
CN XII
hypoglossal nerve
What is the function of CN 1?
olfactory does special sense of smell (olfaction)
What is the function of CN II?
optic- special cense vision
What is the function of CN III?
Oculomotor- motor of extraocular
parasympathetic- ciliary muscle and sphincter pupillae
What is the function of CN IV?
trochlear- motor of superior oblique (extraocular m.)
What is the function of CN VI?
Abducens- motor of lateral rectus
What is the function of CN V1?
general sensory- forehead, surface of eye, bridge of nose
What is the function of CN V2?
general sensory- cheek, upper lip, side of eye
What is the function of CN V3?
general sensory- chin, lower lip, towards temple
motor- muscles derived from pharyngeal arch number 1, mm. of mastication
What is the function of CN VII?
motor- muscles derived from pharyngeal arch number 2
parasympathetics- lacrimal gland, submandibular gland, sublingual gland
general sensory-external ear
special sense- taste and anterior 2/3 of the tongue
What is the function of CN VIII?
Vestibulocochlear n.
special sense- hearing and balance
What is the function of CN IX?
glossopharyngeal n.
motor- muscles derived from pharyngeal arch 3
parasympathetics- parotid gland
general sensory- pharynx, middle ear, carotid body, carotid sinus
special sense- taste to posterior tongue
What is the function of CN X?
motor- muscles derived from pharyngeal arches 4 and 6
parasympathetic- below the neck with parasympathetic etics
general sensory- external ear, larynx
special sense- taste at the epiglottis
What is the function of CN XI?
accessory n.
motor- SCM and traps
What is the function of CN XII?
hypoglossal n.
motor- tongue muscles
What is stern’s rule for the word “tensor”?
CN V3= innervation
What is stern’s rule for the word “palate”?
CN X= innervation
What is stern’s rule for tongue/”glosso”?
CN XII= innervation
What nerves innervate the skeletal muscles of the orbit of the eye?
CN III, IV, VI
What is responsible for pupillary constriction?
Oculomotor n. CN III- parasympathetics
What causes lacrimation to the eye?
Facial n. (CN VII parasympathetics)
What causes blinking?
Ophthalmic n. (CN V1) - sensation to surface of the eye
Facial n. (CN VII)- orbicularis oculi m.
Oculomotor n. (CN III) - levator palpebrae superioris m.
Sympathetics to tarsal muscle
What is nerves are responsible for taste?
facial n. does ant. 2/3 of tongue
glossopharyngeal n. does post. 1/3 of tongue
vagus n. does epiglottis
What is the motor component of the glossopharyngeal nerve?
stylopharyngeus- elevates pharynx and larynx during swallowing and speaking
What do parasympathetics run with to innervate the ciliary m and constrictor pupillae m ?
Oculomotor n.
CN III
What do parasympathetics run with to innervate the lacrimal gland, submandibular gland, and sublingual gland?
facial nerve CN VII
What do parasympathetics run with to innervate the parotid gland?
glossopharyngeal nerve
CN IX
What do parasympathetics run with to innervate postcranial?
vagus n.
CN X
Which nerve is responsible for lacrimation?
facial nerve
Which nerve is responsible for blinking?
ophthalmic n.- sensation to the surface of the eye
What nerve is responsible for the levator palpebrae superioris m?
Oculomotor n.
What innervates the tarsal m?
sympathetics
What nerve is responsible for audition?
inner ear (cochlear n.)
What nerve and muscle is responsible for middle ear function?
mandibular n. and tensor tympani m.
What nerve innervates the stapedius?
facial nerve
What nerve innervates the tensor veli palatini m. or auditory tube function?
mandibular n.
What nerve is responsible for balance (inner ear)?
vestibular nerve coming off of vestibular cochlear
What nerve is responsible for production of nasal mucosa?
facial and trigeminal
What nerve is responsible for laryngeal function?
vagus n.
What are the muscles of mastication?
temporalis, masseter, medial and lateral pterygoids
What is responsible for the tongue movements?
hypoglossal n.
What innervates the palatoglossal m.
vagus n.
What is responsible for taste of the anterior 2/3 of the tongue?
facial nerve –> more specifically the chorda tympani nerve
What is responsible for taste of the epiglottis?
vagus nerve
What is responsible for salivation/salivary glands?
facial- submandibular n. and sublingual n.
What are the primary nerves involved in swallowing?
CN IX, CN X, CN XII
What is considered the true dura in the brain?
the meningeal layer- it is the layer that is continuous down the entire spinal column
Through what nerve is the dura pain sensitive?
intracranial sensory innervation via trigeminal n. and vagus n.
What is the superior sagittal sinus?
a sinus filled with venous blood where the periosteum pulled away from the meningeal layer or true dura
In which space is the CSF?
the subarachnoid space
What is a dural fold?
2 meningeal layers of true dura fused together
What is the purpose of the falx cerebri?
to separate the right and left hemispheres
What is he tentorial incisure
the triangular opening in the tentorium cerebelli through which the brainstem extends from the posterior into the middle cranial fossa
What is the purpose of the cerebellum tentorium?
it separates the cerebral hemispheres from the cerebellum
What are the dural venous sinuses in the brain?
superior sagittal sinus, inferior sagittal sinus, transvers sinus, occipital sinus, straight sinus, sigmoid sinus, superior and inferior petrosal sinuses cavernous sinus
Where do all of the sinuses of the brain meet?
confluence of the sinus
Where is the cavernous sinus in the brain and what are its contents?
Location: lateral to body of sphenoid bone (and sella turcica) Contents: Venous blood Internal carotid a. Nerves: Oculomotor n (CN III) Trochlear n (CN IV) Ophthalmic n (CN V1) Maxillary n (CN V2) Abducens n (CV VI)
What are the purposes of the sinuses?
cerebral veins dump their contents into the dural venous sinuses… they penetrate the arachnoid and pass through subdural space to enter sinuses
subdural hematoma
commonly due to rupture of superior cerebral veins… there is an accumulation of venous blood between arachnoid and meningeal layer of the dura
What are the meningeal arteries embedded within?
the endocranium
epidural or extradural hematoma
most commonly due to rupture of the middle meningeal artery… extravasated blood accumulates between calvarium and cranial dura (periosteal layer)… fatal unless treated promptly
What is the intraventricular flow of CSF?
lateral ventricles –> interventricular foramina –> third ventricle –> cerebral aqueduct –> fourth ventricle –> central canal of spinal cord
How does the CSF exit the ventricular system?
median aperature (foramen of Magendie) --> cisterna magna lateral aperatures --> pontine cistern
How does cerebral spinal fluid absorb back into the dural venous system?
via the arachnoid villi
hydrocephalus
aqueductal stenosis- CSF obstruction at cerebral aqueduct… lateral and 3rd ventricles dilate
What is the non neural basis of visual acuity?
ability to discriminate between adjacent points in an image; non neural is based on the size of image projected on the retina; focus of image by refractive media to the retina
What is the neural basis on visual acuity?
density of photoreceptors in the fovea versus peripheral retina
What are the functions of the eye?
detect light, focus images clearly, compress information
How does the eye detect light?
the central retina (fovea) does details and color… the peripheral retina emphasizes motion and contrast
How does the eye focus on images clearly on the retina?
most of the refraction occurs at the air-cornea interface, there is also an adjustable lens (accommodation) for near objects
sclera
sclera is the fibrous layer of the eye… it is continuous with the dura mater (also considered the white of the eye)
conjunctiva
epithelium lining of inner surface of eyelids and anterior surface of sclera (not part of the fibrous layer)
Iris
dilator pupillae m.
sphincter pupillae m.
ciliary body
ciliary m.; zonule fibers (suspensory ligaments); ciliary processes which form the aqueous humor
choroid
choroidal vessels
What makes up the uveal tract which is the second layer of the eye?
iris, ciliary body, choroid
What makes up the innermost layer of the eye?
retina- part of the eye that is light responsive
What makes up the posterior segment of the eye?
vitreous humor, retina, optic nerve, choroid
What divides the anterior and posterior segment of the eye?
anterior border of the vitreous humor
What part of the eye is affected by light?
peripheral retina and vision, the fovea and central vision
What is the part of the retina that in not neural?
retinal pigment epithelium (RPE)
What is the neural signal path for phototransduction?
through the ganglion cells - Optic nerve
What are the purpose of the photoreceptors in the retina?
they are mostly made up of rods and transform light stimulus into a electrical signal
How do the RPE support photoreceptor function?
by reducing light scatter
How does the peripheral retina deal with motion and contrast?
there are many photoreceptors converging to fewer ganglion cells
What is the purpose of the fovea?
it has the highest density of cone photoreceptors and the least distortion of light
foveation
movements of eye brings light to focus on the fovea
How does the fovea offer maximum discrimination, highest visual acuity, and detail?
there is one photoreceptor for 1 bipolar for 1 ganglion
What artery supplies most of the neural retina (except the photoreceptors)?
the central retinal artery which is a branch of the ophthalmic artery… this arterial supply is absent at the fovea
What artery supplies outer 1/3 of retina ie the RPE and photoreceptors?
choroid
What is the visual consequence of macular degeneration?
central vision will be knocked out… commonly due to cholesterol deposits between the RPE and choroid
What occurs with a retinal detachment?
flashes of light, specks floating, curtain dropping… this typically occurs between the neural photoreceptors and the RPE
Optic disc
axons of ganglion cells (optic n.) and retinal vessels… these lack photoreceptors and the optic disc is considered the blind spot
What kind of information does the optic nerve carry?
information about the entire visual field of that eye
What would happen with a right optic nerve lesion?
complete right eye blindness = right monocular vision loss
What is the image that is displayed on your retina?
inverted (vertically)
revered (horizontally)
Where does the temporal retina receive visual information from?
the medial part of the eyes visual field (nasal hemifield)
Where does the nasal retina receive visual information from?
the lateral part of our eyes visual field (temporal hemifield)
Where do axons from the temporal retina project?
the ipsilateral optic tract
Where do axons from the nasal retina project?
they cross at the optic chiasm and project to the contralateral optic tract
What kind of information does the optic tract carry?
information about the contralateral visual field
right optic tract lesion
left homonymous hemianopia- left visual field of eyes is out
hemianopia
half visual field
homonymous
same side
optic chiasm lesion
Bitemporal hemianopia… lateral fields of both eyes is out… tunnel vision
saccades
right and left eye work in a coordinated fashion… a simultaneous movement of both eyes
What are the functions of the superior rectus?
elevates and intorts
What are the functions of the inferior rectus?
depression and extorsion
What are the functions of the superior oblique?
depressed and intorts
What are the functions of the inferior oblique?
elevation and extorsion
What are the muscles that intort the eye?
superior oblique and superior rectus
What are the muscles that extort the eye?
inferior oblique and inferior rectus
What two muscles must you pair together if you just want to look up or down?
and intort muscle and an extort muscle to balance eachother out
pursuit
allows eye to closely follow a moving object
trochlear nerve
innervates the superior oblique muscle which depresses and intorts
abducens nerve
innervates the lateral rectus muscle which acts to abduct the eye
Oculomotor nerve
superior rectus, inferior rectus, medial rectus, inferior oblique, levator palpebrae superioris
also parasympathetics to the sphincter pupillae m. and ciliary muscle
orbicularis oculi m.
depresses the eyelid and is innervated by the facial nerve
levator palpebrae superioris
elevates the eyelid and is innervated by the Oculomotor
tarsal m.
assists in elevating the upper lid… innervated by sympathetics
what is the purpose of blinking?
to spread tears across the surface of the eye, cornea and conjunctiva
lacrimal gland
secretes into the eye because of innervation done by the facial nerve
what is the excretory process of the lacrimal apparatus?
lacrimal puncta –> lacrimal canaliculi –> lacrimal sac –> nasolacrimal duct –> middle meatus of the nasal cavity
How do the parasympathetics innervate the lacrimal gland?
preganglionic via the facial nerve –> synapse at the pterygopalatine ganglion –> postganglionic they travel on the trigeminal nerve
What is the sensory limb of the coronary blink reflex?
there is irritant to the cornea/ conjunctiva which sends nerve signals via the nascociliary n. a branch from ophthalmic n.
What is the motor limb of the sensory light reflex?
the nerve signals are sent to the eye via the facial nerve to the orbicularis oculi m.
strabismus
misaligned visual axes (due to a neural/motor imbalance usually
diplopia
double vision
if a patient is unable to abduct the right eye what kind of lesion is it?
abducens lesion on the right side
What are the consequences of a unilateral lesion of R. abducens N?
the lateral rectus muscle is paralyzed
diplopia occurs due to unopposed medial rectus m.
face also turns to side of lesion to restore binocular vision
upper lid ptosis
inability to retract the upper eyelid (eyelid is depressed)
What are the characteristics of a unilateral lesion of a R. Oculomotor n. lesion?
eyelid is depressed and the eye is turned laterally and slightly down… there may also be mydriasis which is a dilated eye
Oculomotor palsy
upper lid ptosis extropic globe (down and out) strabismus and diplopia mydriasis (dilated pupil) lack of accommodation
Trochlear nerve palsy
extorted eye and impaired depression because there is paralysis of the superior oblique
unilateral lesion of the r. trochlear n.?
extorted right eye results in diplopia
head tilt to unaffected side (point chin to lesion)
intort L. eye to restore binocular vision
horner’s syndrome
interruption of sympathetic outflow: upper lid ptosis (tarsal m. paralysis) miosis (constricted pupil) facial flushing (vaso dilation) Anhidrosis (sweat gland denervation)
focusing on a near object triad
. Convergence of optic axes (somatic motor)
Oculomotor nucleus signals both medial rectus mm. to contract (disconjugate eye movements) to eliminate diplopia
2. Lens Accommodation (parasympathetic)
Oculomotor efferent axons from Edinger-Westphal nucleus signal ciliary m. to contract to eliminate blur
Reduce tension of suspensory ligaments of lens
Curvature of lens increases (higher refractive index)
3. Pupillary constriction (parasympathetic)
Oculomotor efferent axons from Edinger-Westphal nucleus signal sphincter pupillae m. to contract
Small pupil sharpens image on retina and reduces light intensity
What is the muscle that lies in the superficial cervical fascia?
platysma m.
What are the muscles that lie in the deep cervical fascia the investing layer?
SCM m. and the trapezius m.
What are the anterior and posterior triangles of the neck subdivided by?
suprahyoid and infrahyoid m.
What is included in the vertebral compartment?
includes CVs and mm. for neck movement and stability… is also surrounded by vertebral fascia
What are the cutaneous nerves for the cervical plexus?
transverse cervical n.
supraclavicular n.
greater occipital nerve
lesser occipital nerve
what is the motor innervations from the cervical plexus?
mm. of neck, infrahyoid muscle, and diaphragm
What is in the vascular compartment of the deep cervical fascia?
carotid aa., internal jugular v, vagus nerve… which are all surrounded by the carotid sheath
What are the layers within the visceral compartment of the deep cervical fascia?
endocrine layer- thyroid gland, parathyroid gland
respiratory layer- larynx, and trachea
alimentary layer- pharynx: nasopharynx, oropharynx, laryngopharynx and the esophagus
What does the deep neck spaces consist of?
buccopharyngeal fascia, alar fascia, prevertebral fascia
retropharyngeal space
between the buccopharyngeal fascia and the alar fascia… at the base of the skull to superior mediastinum
danger space of the neck
between the alar fascia and the prevertebral fascia… base of skill to diaphragm
What encloses and protects the middle and internal ear?
temporal bone
where does conductive hearing loss happen?
middle and external ear
Where does sensorineural hearing loss happen?
inner ear
What innervates the superior external acoustic meatus?
auriculotemporal nerve from the mandibular division of trigeminal
What innervated the inferior external acoustic meatus?
vagus nerve
What innervates most of the outer ear?
greater auricular n. (C2-C3)
What is the innervation of the auricle?
auriculotemporal n.
vagus n.
facial n.
two cervical nerves: greater auricular n. and the lesser occipital n.
What is the innervation of the tympanic membrane in the lateral surface?
superiorly it is innervated by the auriculotemporal n.
inferiorly it is innervated by the vagus
What makes up the inner ear?
tympanic cavity
ear ossicles: malleus, incus, stapes (lateral to medial)
What are the muscles in the middle ear?
tensor tympani innervated by mandibular nerve
stapedius innervated by facial nerve
What are the walls of the middle ear?
laterally it is the tympanic membrane; medially there is the promontory and oval and round windows
What is the roof of the middle ear?
tegman tympani
What is the flood of the middle ear?
jugular bulb
What is the posterior wall of the middle ear?
mastoid air cells
what is the anterior wall of the middle ear?
pharyngotympanic, Eustachian and auditory tube
What is the function of the Eustachian tube?
ventilations and pressure regulation; by the tensor veli palatini m.
In cleft palate patients where would there be a dysfunction?
in the tensor veli palatini muscle
What is the function of the tensor veli palatini?
it actively widens the lumen
What is the protection function of the Eustachian tube?
dampens loud sounds from the nasopharynx; active against reflux of nasopharyngeal secretions
What is the drainage and clearance function of the Eustachian tube?
mucociliary transport system
What is the function of the glossopharyngeal n. in the ear?
sensory via the tympanic nerve plexus… tympanic cavity, tympanic membrane, mastoid air cells and the auditory tube
Where does the chorda tympani nerve pass through?
pas between the malleus and incus
conductive hearing loss?
external ear… cerumen impaction
middle ear is otitis media
what is the primary cause of otitis media?
dysfunction of the Eustachian tube
What makes up the inner ear?
semicircular canal, vestibule, cochlea
What is the membranous labyrinth of the inner ear?
cochlear duct in cochlea, utricle and saccule in the vestibule, semicircular duct in the semicircular canal
What makes up the neurosensory epithelium?
organ od corti on basilar membrane in the cochlea, macule in the vestibule, the crista ampullaris in the semicircular canal
How does the transmission and transduction of sound work?
air pressure waves and transduced to mechanical energy that is transduced to fluid movement in the inner ear
basilar membrane
determines the frequency of the sound that we hear
What is the first sign of compression of the Oculomotor nerve?
slowness of the pupillary response to light
What stimulates the organ of Corti?
the basilar membrane
Where does the ability to hear high frequencies occur?
at the base of the basilar membrane
Where does the ability to hear low frequencies occur?
the apex of the basilar membrane
impedence mismatch
When there is low air impedence and high fluid impedence you lose 99.9% of sound energy
How are incisions to release pus from a middle ear abscess made?
postero-inferiorly because the superior half is much more vasculature
What are the solutions to impedence mismatch?
external ear amplification
middle ear amplification- because of large surface area of the tympanic membrane going to the footplate of the stapes
What overlays the oval window?
the stapes
What is the solution to localization of sound?
binaural comparisons
What helps to solve the problem of loud noises?
there is middle ear dampening- done by the tensor tympani muscle innervated by mandibular nerve also the stapedius muscle which is innervated by the nerve to the stapedius off of the facial nerve
What is the acoustic (Stapedial reflex)?
the afferent limb in done by the cochlear n. (bilaterally) and the efferent limb is done by the facial n. (direct and consensual)
What do we do to fix the issue of complexity of sounds?
the left ear hears music and goes to the right hemisphere… the right ear hears spoken communication and goes to the left hemisphere
What helps us control our balance?
vestibular apparatus- made up of the vestibule and semicircular canals and the saccule and utricle and semicircular ducts
What is the purpose of the saccule and utricle?
they sense gravity and linear movement or acceleration
what is the purpose of the semicircular ducts?
rotational movement (angular acceleration)
What comprises the lateral nasal wall?
inferior middle and superior turbinates
What gives sensory innervation to the nasal cavity?
trigeminal nerve ophthalmic and maxillary nerves off of the trigeminal
Where do autonomics travel to access the nasal mucosa?
sympathetics and parasympathetics travel on the trigeminal nn.
What is the airflow resistance between the two nasal cavities controlled by?
sympathetics… the engorgement by blood of the anterior ends of the inferior nasal turbinates
Where do all of the arteries of the nasal septum converge?
kiesselbach area- branch of Sphenopalantine artery and posterior and anterior ethmoidal arteries… this causes anastomosis between the ECA and the ICA
What are the paranasal sinuses?
frontal sinus, ethmoid sinus, nasal cavity, maxillary sinus
where does the sphenoidal sinus drain?
sphenoidal recess
What drains into the superior meatus?
posterior ethmoidal cells
What all drains into the middle meatus?
anterior and middle ethmoidal cells through the ethmoidal bulla and the frontal and maxillary sinus through the semilunar hiatus
What drains into the inferior meatus?
nasolacrimal duct
Which paranasal sinus has the most difficulty draining?
maxillary sinus
Why does the maxillary sinus drain poorly?
because its ostium is located superiorly… dental pain may be indicative of maxillary sinus
