Hearing and Vestibulation Flashcards
auricle
- this is the ecternal ear structure
- also called the pinna
- creates a funnel to the external acoustic meatus
- this protects the opening passage way and provides sensitivity to the ear by directing sound inward to the tympanic membrane
external acoustic meatus
a passageway in the temporal bone that leads to the tympanic membrane of the middle ear
tympanic membrane
this is the eardrum
- this separates the external auditory meatus and the middle ear
- this is a thin semi transparent CT that separates the external and middle ear
- this is what leads to the movement of the ossicles
cerumen
- this is ear wax
- this is secreted by ceruminous glands and these are modified sweat glands
- this functions to protect the ear and lubricate the ear
external ear
- this consists of the auricle, external acoustic meatus, and the tympanic membrane
- also contains elastic cartilage
middle ear
- this is the air filled tympanic activity that is between the tympanic membrane and the internal ear
- contains the auditory ossicles
malleus
- an auditory ossicle
- this is the ossicle that is bound to the tympanic membrane
incus
- an auditory ossicle
- this connects the malleus and the stapes
stapes
- an auditory ossicle
- this is connected to the inner ear
- the footplate almost completely covers the oval window in the bony wall of the middle ear
describe the movement from the tympanic membrane to the inner ear
- the tympanic membrane converts arriving sound waves into mechanical movements and the mechanical movements vibrate the Malleus, which vibrates the incus, which vibrates the stapes and effects the fluid of the inner ear
what is important about the type of joint of the ossicles
- the joints are synovial joints and this allows the movements to be in and out movements
- this type of moment is amplifying the movement of the tympanic membrane
inner ear
a labyrinth that contains the organs or hearing and equilibrium
- this is divided into two regions (the region for vestibulation and the region for hearing)
pharyngotympanic tube
this is a connection between the nasal cavity and the middle ear
- this is designed to allow for equalization of pressure in the middle ear with the atmosphere
otitis media
this is an infection in the middle ear
- this is different than swimmers ear or an outer ear infection
- this is caused by a blockage of the pharyngotympanic tube
- this is more common in children because their tube is more horizontal and as we age it becomes more vertical
- if people consistently get an otitis media, they can go through a procedure to get a tube placed in
perforated eardrum
- this is when there is a rupture in the ear drum
- this can be caused by a physical trauma to the eardrum, a middle ear infection, or changes in pressure
- this is why it is important for scuba divers and snorkelers to learn how to equalize their pressure at certain depths
bony labyrinth
- this is within the temporal bone and surrounds and protects the membranous labyrinth
- this is filled with perilymph
- this consists of the vestibule, the semicircular canals, and the cochlea
membranous labyrinth
- this is encased in the bony labyrinth and the perilymph
- this is filled with endolymph
- this can be divided into the vestibular complex (saccule and utricle) and the cochlear duct
perilymph
this is within the bony labyrinth and this surrounds the membranous labyrinth
- this is similar to CSF
endolymph
this is within the membranous labyrinth
vestibule
a chamber within the internal ear
- this is the site of vestibulation
- this contains the utricle, saccule, and semicircular ducts
vestibulation
this is the understanding of how the head is moving in space
cochlea
this is the spiral portion of the bony labyrinth of the internal ear that surrounds the hearing portion
- this is divided into three channels: cochlear duct, the scala vestibuli and the scala tympani
tensor tympani
- this is a short muscle in the middle ear that originates on the petrous part of the temporal bone
- innervated by the mandibular division of the trigeminal nerve
- a skeletal muscle
- works to tense the ossicles and prevent forceful movements under very noisy conditions
stapedius
- a muscle in the middle ear
- this is the smallest skeletal muscle in the human body
- this works to pull the stapes and reduce movement at the oval window
- innervated by the facial nerve
- works to tense the ossicles and prevent forceful movements under very noisy conditions
utricle
the largest chamber of the vestibular apparatus of the internal ear
- this contains a macula that provides sensations about acceleration in the horizontal direction
- this would be forward, backward, or side to side
saccule
a portion of the vestibular apparatus of the inner ear
- this contains a macula that provides sensations about linear acceleration in the vertical direction
- this would be up and down movements
macula
this is the portion of the utricle or saccule that contains the hair cells
otolithic membrane
this is the gelatinous layer within the vestibule
- the hair cells are embedded within
- contains otoliths
otoliths
these are densely packed calcium carbonate crystals embedded in the gelatinous matrix
- these are there to weigh down the gelatinous layer
ampulla
this is the expanded region of each semicircular canal
- this contains an elevated region covered by hair cells (the sensory receptors)
hair cells
these are the sensory receptors of the internal ear and are monitored by afferent fibers
- these are highly specialized mechanoreceptors
- the hair cells bend, they become depolarized and this causes the stimulation of the vestibulocochlear nerve (CN VIII)
semicircular canals
there are three of these:
- anterior
- posterior
- lateral
they all contain an ampulla and a cupula
- these are continuous with the vestibule and surround the semicircular ducts
semicircular duct
- this responds to movements of the head based on the movement of the endolymph within
- these are continuous with the utricle
- these are surrounded by the semicircular canals
anterior semicircular duct
- this responds to movement in the saggital plane
- this would be the “yes” movement
posterior semicircular duct
- this responds to movement in the coronal plane
- this is tilting the head toward the shoulder
lateral semicircular duct
this is responding to movement in the transverse plane
- this is the “no” movement
what happens when the head is rotating in the plane of the duct
- the rotational acceleration causes the endolymph to move and deform the gel layer (cupula)
- this then stimulates the fibers of the vestibular portion of the CN VIII
cupula
this is an overlying gelatinous dome that the hair cells are embedded in
describe what happens with linear acceleration
- when the body accelerates, the gel layer will move backwards in response to inertia and this movement lets the body know that it is moving forward
- the otoliths push on the gel and this bends the hair cells
scala vestibuli
- this contains perilymph
- this is adjacent to the vestibular membrane
- the fluid in this channel is what is stimulated initially by the movements of the stapes at the oval window
scala tympani
- this contains perilymph
- this is adjacent to the basilar membrane
- the fluid here is what gets stimulated after the movement of the spiral organ and causes the dissipation of movement at the circular window
cochlear duct
this is a tube within a tube
- this has the vestibular membrane, the basilar membrane, the spiral organ, and the tectorial membrane
vestibular membrane
this is the roof of the cochlear duct
- this is adjacent to the scala vestibuli
basilar membrane
this is the floor of the cochlear duct
- this is what the spiral organ is on
- this is adjacent to the scala tympani
spiral organ
this sit s on the basilar membrane of the cochlear duct and this is ultimately responsible for the stimulation of the cochlear portion of CN VIII
- this detects movements of the endolymph
- it is a thick sensory endothelium with hair cells
tectorial membrane
- this is an overlying gel mass that the hair cells project into
describe how the spiral organ detects movement
- the fluid in the cochlear duct moves in response to the movement in perilymph of the scala vestibuli
- this movement of fluid in the cochlear duct causes movement of the spiral organ
- as the spiral organ moves, the hair cells bend and this leads to depolarization and stimulation of the nerve cells
describe the movement of sound waves through the ear
- the sound waves come in and hit the tympanic membrane causes it to move
- the ossicles move in response
- the oval window vibrates
- the perilymph in the scala vestibuli moves
- the endolymph within the cochlear duct begins to move
- the basilar membrane and spiral organ vibrate
- this leads to sending info to the cochlear branch of CN VIII
- the perilymph in the scala tympani moves as the movement from the cochlear duct dissipates here
- the perilymph dissipates its movement onto the round window
describe the CNS auditory pathway
- the basilar membrane and the the spiral organ stimulate the cochlear part of the CN VIII
- the axons of CN VIII travel and synapse at the cochlear nuclei in the brainstem
- this signal is then sent to the inferior colliculi
- then ascending sound information goes to the medial geniculate nucleus
- then projection fibers deliver info to specific locations within the auditory cortex of the temporal lobe
inferior colliculi
- this are responsible for unconscious motor responses
- causes you to turn the head when you hear something
what does a hearing aid do
- this is something used to help amplify sound coming in because there is likely damage to the external ear or middle ear
- the cranial nerve 8 is still working properly
cochlear implant
- this is placed because there is something wrong in the pathway that is leading to a lack of stimulation of CN VIII
- whatever the issue is, this implant bipasses the structures and stimulates the nerve to give sense of hearing
describe the CNS pathway of vestibulation
- the vestibular portion of CN VIII is stimulated and sends info to the vestibular nuclei (medulla)
- this then integrates sensory information and sends it to:
- cerebellum
- cerebral cortex
- CN III, IV, VI, XI
- spinal cord
what is the importance of the integration of sensory information and it being sent to the cerebellum in the CNS pathway of vestibulation
- this is smoothing out muscle movements and working on balance and coordinated movements
what is the importance of the integration of sensory information and it being sent to the cerebral cortex in the CNS pathway of vestibulation
- this is telling the brain what happened
what is the importance of the integration of sensory information and it being sent to the CN III, IV, VI, XI in the CNS pathway of vestibulation
this is back to other CN because these are related to:
- ocular movements (when you are spinning around and stop the first thing you try to do is find an object to focus your gaze
- movements of the shoulder (stops your head from moving)
what is the importance of the integration of sensory information and it being sent to the spinal cord in the CNS pathway of vestibulation
- this is sending info to the legs to stabilize the body and stop moving, plant feet, flex quads etc
stereocilia
80-90 long appendages that resemble microvilli on the hair cells
kinocilium
a single large cilium on each hair cell
- these are not found in the cochlea
oval window
this is an opening in the bony labyrinth where the stapes attached to the membranous wall of the vestibular opening
round window
this is an opening in the dense bone wall of the cochlear spiral
- this is inferior to the oval window
- this is where the movement of the perilymph within the scala tympani dissipates
- this is a thin membranous partition that separates the perilymph
high frequency sounds are perceived where
- these are perceived just proximal to the oval window
low frequency sounds are perceived where
closer to the apex of the cochlea
endolymphatic sac
- this projects through the dura mater lining the temporal bone
- this is surrounded by a capillary network and this is where the excess fluid that is produced is returned back into general circulation
- this branches off a slender passageway that connects the utricle and the saccule
