Auditory and Vestibular system (CN VIII) Flashcards
CN VIII has 2 divisions, what are they
cochlear - sound
vestibular - head position and movement
what is the name of the mechanoreceptor cells of the auditory and vestibular system
hair cells
the auditory and vestibular systems are both embedded w/in what bone
temporal bone
The bony labyrinth is composed of what ?
- cochlea (coiled thing)
- vestibule
- 3 semicircular canals
the membranous labyrinth is composed of ?
- cochlear duct
- utricle (connected to semicircular ducts)
- saccule (connected to cochlea and utricle)
- 3 semicircular ducts
what is the fluid that fills the bony labyrinth and what is it similar to
perilymph, similar to CSF
what is the fluid that fills the membranous labyrinth what is it similar too
endolymph, similar to intracellular fluid
what seperated the perilymph from the endolymph, AND why are they significant
tight junctions - create membrane potentials from the difference in ion conc.
hair cell microvilli are known as ______
stereocilia
what is the name given to the tallest stereocilia
kinocilium
what region of the auditory and vestibular systems has hair cells that lack kinocillia
cochlea
what is the cause of Meniere’s disease
obstruction of flow resulting in swollen membranous labyrinth
the tips of the kinocillia are embedded into ?
gelatinous material
how are hair cell receptors transduced
movement in the gelatinous material causes deflection of the sterocillia = receptor potential transduced
deflection towards the tallest sterocillia causes
depolarization of the hair cell
deflection away from the tallest sterocillia causes
hyperpolarization of the hair cell
deflection perpendicular to the sterocillia causes
nothing, no effect
what is the role of the outer and middle ear
convey airborne sound vibrations to fluid filled inner ear
what are the 2 muscles of the middle ear and what is their main function
- stapedius - pull stapes away from oval window = stiffening
- tensor tympani - pulls malleus toward middle ear = stiffeneing
- * Both work to stiffen ossicular chain**
the _____ m. blocks the sounds of your own voice, whereas the _____ m. blocks chewing sounds
stapedius
tensor tympani
what middle ear muscles innervated by
- stapedius - CN VII
- tensor tympani - CN V
What are the 3 components of the structure of the Cochlea, and what type of lymph resides within each
1 - scala vestibula - perilymphatic space
2 - scala media - endolymph
3 - scala tympani - perilymphatic space
where does the scala tympani end ?
Ends blindly at the round window
where is the organ of corti in the ear
rests on basilar membrane of the cochlea, w/in the stri media
what is the spongy bone w/in the cochlea called
modiolus
what are the 2 groups of cells found in the organ of corti
- inner hair cells - unattached to tectorial membrane
- outer hair cells - attached to tectorial membrane
what is the difference b/w the inner and outer hair cells of the organ of corti on how they become stimulated
- inner (unnattached) stimulated by endolymph movement across sterocilli
- outer (attached) stimulated by vibrations in basilar membrane
movement of ______ causes a pressure pulse in the scala vestibuli of the organ of corti, which leads to a traveling wave of deformations in the ________
stapes at the oval window, basilar membrane
Explain “mechanical tuning”
the tonotopic organization of the auditory system based upon the amplitude and frequencies of waves on the basilar membrane
cochlear implants are based upon the tonotopic org. of the auditory system. With that said we place a coil of electrodes where to stimulate the intact CN VIII nerve endings
round window into the scala tympani at different points along the basilar membrane
CNS auditory processing analyzes what ?
sound frequency and intensity
what is the primary ascending pathway in CNS auditory processing
lateral lemniscus pathway
the lateral lemniscus pathway has fibers that will first synapse at the ____________ nucleus, then at the ______, then project to the inferior brachium and ending at the _________ nucleus
- superior olivary nucleus —–> inferior colliculus
- ——> medial geniculate nucleus of the thalamus
where is the primary auditory cortex anatomically on the brain
transverse temporal gyri
distinguish bc gyri run mediolaterally vs. front to back
T/F Sound that reaches the left ear before the right will be heard softer and less intense
F , will be heard louder and more intense
IN CNS auditory processing what it the nucleus important in sound localization
superior olivary nucleus
T/F the lateral lemniscus pathway carries information from both ears ?
True
what is an audiogram
way to meausre someones threshold for hearing via
- headphones (air conduction)
- vibration (bone conduction)
what is the difference b/w a conductive hearing loss and a sensorineural hearing loss
conductive is when sound cant reach labyrinth
sensorineural is when there is damage to hair cells or cochlea nuclei
in an audiogram, air conduction (headphones) needs and intact _____________ ?
outer, middle, and inner ear
a defect in bone conduction is usually the result of ?
sensorineural problem
the most common air conduction defect is the result from
middle ear infection
what detects angular acceleration of the head
semicircular ducts
one end of each semicircular duct closest to the utricle is called the
ampulla (which contains the crista)
sterocillia hair cells in the semicircular ducts are arranged in a transverse called the _________ and extend into a gelatinous mass above called the ____________
crista
cupula
deflection of the cupula leads to increase afferent firing in the semicircular ducts. During deflection as rotation begins, what is laggin behind which deflects the cupula and inevitably stimulates the sterocilla hair cells
endolymph lags behind during rotation
if rotation in the semicircular duct continues what happes
endolymph catches up and no deflection of the cupula occurs
what detects linear acceleration in the vestibular system
utricule and saccule
what is the difference in the arangement of macula and sterocillia in the utricle and saccule?
utricle - macula horizontal and sterocilla face up
saccule - macula vertical and sterocilla face laterally
what is the otolithic membrane and where is it found
a dense gelatinous material of the macula in the utricle and saccule (more dense than endolymph)
what is the difference b/w the utricle and the saccule with regards to what direction of linear acceleration they can detect
utricle - forward/backward and side to side
saccule - forward/backward and up/down
what is the primary afferent cell body in the internal auditory canal that has vestibular projections
Vestibular ganglion (Scarpa’s ganglion)
The Vestibular nuclei has output to where ?
spinal cord
VPL of thalamus to cortex
braintstem
vestibulospinal fibers that have excitatory projections to antigravity muscles follow what tract ?
lateral vestibulospinal tract
vestibulospinal fibers that stabalize head movements as we walk and coordinate head/eye movements travel on what tract ?
medial vestibulospinal tract
the vestibular system works to prevent images from moving on the retina (keep images on the retina), this is known as _____________
Vestibuloocular reflex (VOR)
what is the afferent and efferent limb of the vestibuoocular reflex
afferent - CN VIII
efferent - CN III, IV, VI
what is nystagmus
rapid eye movements in the opposite direction bc the VOR cant compensate for head movements
alcohol has the ability to alter the density of the ______ and ______ making semicircular ducts sensitive to gravity
cupula and endolymph (the spins when your drunk)
what is Rombergs sign
when patient closes eyes and loses balance
the posstion sense is mediated by what 3 systems working together
1 - vestibular
2 - proprioceptive
3 - visual
