Hearing Science Exam 2

what problem does middle ear polarization function fix?

how to allow for motion of the cochlear liquids inside closed capsule by having 2 windows to inner ear with mechanical stimulation at oval window

what does the round window reciprocating response in the middle ear allow for?

it allows for displacement of cochlear liquids causing wave action stimulated by rocking motion of footplate of stapes

what is the middle ear ventilation and pressurization problem and what is the solution?

problem is the tympanic cavity is closed, air-filled cavity and the solution is that periodically open airway via eustachian tube

what muscles are used during swallowing, yawning, and chewing?

both tensor veli palitini and levator veli palatini

what is the opening for swallowing, yawning, and chewing?

at toros tubarius in nasopharynx

what does swallowing, yawning, and chewing do?

places TM in proper position and prevents unhygienic environment

eustachian tube dysfunction may lead to

a lack of middle ear aeration

what can a lack of. middle ear aeration lead to?

tympanic membrane retraction, chronic otitis media, hearing loss with language delay in children, chronic tympanic membrane perforations, or cholesteatoma

what is a cholesteatoma?

an abnormal skin growth in the middle ear

if a cholesteatoma is allowed to increase in size what might happen?

it may destroy the ossicular chain and in rare cases may also result in a permanent hearing loss, dizziness, and facial muscle paralysis

what problem does the middle ear protection/distortion control function seek to solve and how does it solve it?

the problem is protect inner ear from mechanical overstimulation and the solution is to increase tension of ossicular chain in order to reduce the low frequency sound intensity that reaches the cochlea

what is the mechanism of middle ear protection/distortion control function

the acoustic reflex is stimulated by eating, talking, yelling, other vocalizations, and exposure to high-level sounds. primarily, the stapedius muscle is contracted which stiffens the ossicular chain and reduces the sound reaching the cochlea

what is the efferent acoustic reflex pathway?

descending path from brainstem to stapedial muscle via VIIth (facial) nerve

what is the afferent acoustic reflex pathway?

ascending path from cochlea to brainstem via VIIIth nerve?

what is the acoustic reflex pathway?

from the inner ear (cochlea) to the ventral cochlear nucleus to the superior olivary complex to the facial nerve to the stapedius

what are the x and y axis for measuring the acoustic reflex response?

x axis is time

y axis is admittance or flow of sound energy into the middle ear

why is the acoustic reflex threshold determined and why is it used?

it's determined to measure the function of the acoustic reflex pathways and is used in part to determine the site of lesion for auditory disorders

sound reduction is provided by

the acoustic reflex

are low or high frequency sounds more attenuated (reduced)?

low frequency

what is maximum benefit for low frequencies?

20-30 dB

after the experiment, the stapedius reflex was functional or not functional in response to the highest level sounds?

functional

in rabbits with one ear with and one ear without functioning midle ear muscles, the ear without functioning MEMs had more what than ear with functional MEMs?

extensive damage

exercise ___ the stapedial reflex and ___ the risk of a temporary threshold shift, resulting in what?

depresses, increases, temporary hearing loss

what happens for the stapedius reflex to kick in?

loud sound and mostly a low frequency

which frequency region is found at the base?

high frequencies

what is the middle of the cochleus?

modiolus

cochlea turns around the

modiolus

what neurons conect to the hair cells

afferent and efferent neurons

what are habenula perforatum

holes in the osseous spiral lamina

what attacks high frequency and can cause hearing loss?

noise exposure, old age, sometimes genetics, some cancer drugs are oditoxic

what covers the tops of the hair cells

reticular lamina (a thin layer of connective tissue)

tectorial membrane covers

stereocilia of the hair cells

what are some characteristics of inner hair cells?

pear or flask shaped

approximately 3,500

single row

centralized nucleus

organelles distributed throughout the cell body

no motility

what are stereocilia like in the inner hair cells?

they are not attached to the tectorial membrane and are in crescent shape

what are some characteristics of outer hair cells?

cylindrical shape

approximately 12,000

3 rows

nucleus found in base

organelles found along the outer walls

"stretch and shrink" OHC motility

what are stereocilia like in the outer hair cells?

they are attached under the tectorial membrane and are in W or V shape

what are neurons like in inner hair cells?

95% of the afferent neurons

many afferent neurons connect to each IHC

afferent neurons synapse with cell body while efferent neurons synapse with the afferent neurons

what are neurons like in outer hair cells?

5% of afferent neurons

each afferent neuron (outer spiral fibers) connects to many OHCs

efferent and afferent neurons synapse directly with cell body

efferent neurons synapse with the _______, while afferent neurons synapse with ____

afferent neurons, IHC

efferent and afferent neurons synapse directly with

the OHC

each afferent neuron (outer spiral fibers) connects to many

OHCs

type 2 fibres synapse with up to

50 OHCs

many type 1 fibres synapse with ______ directly opposite their habenular opening

one IHC

the features of the cochlea imply a complex systen that is

mechanical (vibrator motion)

hydraulic (wave motion)

chemo-electrical (nerve energy)

what is the role of the semicircular canal?

to sense movement of the head, both speed and direction

how many semi circular canals are there?

3

what are the two parts parts of the vestibule?

the saccule and utricle

where is the utricle located?

superior to the saccule

what are the utricle and saccule used for?

to detect the orientation of the head, ex. tipped down or up, or tilted to one side

what is the cochlea?

it's closed, labryrinthine capsule, filled with fluid

where is the cochlea?

inner ear in petrous portion of temporal bone; it's the most anterior structure

what is the cochlea named for?

the sea snail that its shape resembles

what is the auditory branch of the 8th nerve?

large bundle of nerve cells that enters the center of the cochlea

how many turns is the bony labrynth?

2 5/8th turns

are schematic of the cochlea stretched or coiled?

stretched, note the tube inside the canal

what are the 3 major anatomical components of the inner ear?

semi circular canals, vestibule, and the cochlea

what is the bony canal?

it's like a spiral staircase that turns around the modiolus

what is the modiolus?

the center of the cochlea with solid bone walls

auditory nervefibers from the hair cells enter the

modiolus

what is the line that passes through the modiolus?

the center of the cochlea

what does Reissner's membrane separate?

the scala vestibuli and the scala media

what is the organ of corti?

discovered by Alfonzo Corti, in the middle scala of the ear, the actual hearing apparatus

what does the organ of corti hold?

outer and inner hair cells and tectorial membrane

labeled organ of corti

the human ear is not sensitive to sounds outside

20-20,000 Hz

what is the tectorial membrane

part of the scala media that covers the inner and outer hair cells along the basilar membrane

nerve cells attach to the

cell body

how many turns is the bony labyrinth

2 5/8ths

how long is the base to the apex of the bony labrynth

35 mm (about 1' long)

where does the labyrinth of the cochlea end?

at the helicotrema in the apex

the base of the cochlea is near the ____ while the apex is where?

stapes footplate, apex is at the other end of the bony labyrinth

what is paralymph?

fluid in both the oval and round windows

what happens at the helicotrema?

the scala tympani and scala vestibuli meet

what is the osseous spiral lamina?

bony extension of the medial wall of the bony labyrinth, runs continuously along the medial wall

what are the holes in the osseous spiral lamina called?

habenulae perforata

the width of the osseous spiral lamina ____ between the base and apex of the cochlea

decreases

by the time the cochlea reaches its third turn, the osseous spiral lamina has nearly

disappointed/disappeared

3 sections/scalas of the mebranous labyrinth

scala vestibuli, scala media, scala tempani

characteristics of the scala vestibuli

bounded inferiorly by Reissner's membrane

ends at helicotrema

contains perilymph

where are the spinal ganglion and what does it do?

in the modiolus and houses lots of cell bodies together

where does the 8th nerve come out of?

the spiral lamina and then goes into the internal auditory meatus

outer hair cells are on the ____ side of the scala media of the basiliar membrane of the cochlea

lateral

what is the auditory nerve and where does it attach?

the 8th nerve which is a bunch of nerve cells together attached to the cochlear nucleus

what do neurons, nerve cells, and nerve fibers attach to

inner and outer hair cells

what is a vestibule

a small entrance hole

what is the scala vestibuli bounded by?

inferiorly by Reissner's membrane

what is the scala tympani bounded by?

bounded superiorly by basilar membrane

where does the scala tympani end?

at the helicotrema

what does the scala tympani contain?

perilymph

does the width of the basilar membrane increase or decrease between the base and the apex of the cochlea?

increase

what does the increase in width (and in mass) of the basilar membrane correspond with?

the decrease in the width of the osseous spiral lamina (to which the basilar membrane is attached to on its medial surface)

damage at the cochlea can cause

low frequency hearing loss and voiceless fricative hearing problems

noise exposure, old age, odotoxic medications can damage what part of the cochlea?

high frequencies (at the base)

what is the scala media bounded by?

bounded superiorly by Reissner's membrane and inferiorly by basilar membrane

what does the scala media contain?

the organ of corti and endolymph

is the osseuous spiral lamina closer to the inner or outer hair cells?

closer to inner hair cells

how do the scala vestibuli and scala tympani share perilymph and what keeps the endolymph in the scala media?

Reissner's superiorly and basilar membrane inferiorly

perilymph is shared at

helicotrema

what are the attachments for the basilar membrane

spiral ligament on lateral side, osseous spiral lamina on medial side

what are on top of the osseous spiral lamina?

fibrous stiff cells