More Middle Ear
About this set
Created by:
AbraMarcum on November 15, 2011
Subjects:
Anatomy of the speech and hearing mechanism
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53 terms
Terms | Definitions |
|---|---|
 what is the ratio of impedence of cochlear fluid and air? | 4000:1 |
| w/o the ME, how much sound would be reflected back? (% and dB) | 99.9% 30-35 dB |
| w/o the ME, how much energy would be lost? | 30-35 dB |
| How does the ME overcome the impedence mismatch? | 1. areal ratio (17:1) 2. curved membrane ratio (2:1) 3. ossicular lever ratio (1:3:1) |
| how big is the part of the TM that vibrates? | 55mm |
| what is the areal ratio? | 17-1 (so, pressure is amplified 17 times from TM to footplate) |
| what is the area of the footplate? | 3.2mm |
| Total transmission ratio of the ME | 46:1 (46 times more pressure ant footplate than at TM) =33 dB gain |
| how much hearing loss CAN the ME cause i it is sick or absent | 40-60 dB conductive hearing loss |
| does a normal ME have impedence? | yes |
| at 80-90 db, stapedius and tensor tympani have what? | bilateral, consensual reflexive contraction -they attenuate sound by 10-30 dB |
| what does the tensor tympani reflex in reaction to? | puff of air in eye bc od CN V |
| ME pathologies | 1. otosclerosis 2. ossicular disconinuity 3. frozen ossicular chain |
| otosclerosis | -increases impedance -begins with vascular spongiosis, eventually replaced with sclerotic plaques -stapes becomes fixed in oval window -an early sign is Schwartze's sign (bluish-red tint near promontory due to increased vascularization) -characteristic notch at 2000 Hz (carhart's notch) |
| ossicular discontinuity | -broken ossicular chain -causes decreased impedance TM can vibrate freely -trauma |
| frozen ossicular chain | increased impedance |
| What part of the temporal bone is the inner ear located in? | petrous portion |
| 3 parts of the inner ear | 1. cochlea 2. vestibule (utricle/saccule) 3. semicircular canal |
| Bony labyrinth | canals through temporal bone -lined by membranous labyrinth |
| how many turns does the cochlea take? | between 2.2-2.9 turns |
| what are the measurements of the cochlea? | 1 cm wide 5 mm from base to apex |
| modiolus | central core of cochlea that eventually becomes CN VIII (has nerve fibers from the hair cells and blood vessels) |
| osseus spiral lamina | -shelf-like structure that winds around the modiolus |
| helicotrema | apex of the cochlea where the two scalas meet |
| where is the oval window? | at the opening of the scala vestibuli (the most superior duct) |
| round window is located | -at the basal-most aspect of the scala tympani (most inferior duct) |
| reissner's membrane separates | separates scala media from scala tympani |
| basilar membrane separates | separates scala media from scala vestibuli |
| ductus reuniens of hensen | how scala media communicated w/the vestibular portion of the inner ear (at the basal region) |
| what does the stria vascularis do? | produces endolymph |
| how is the basilar membrane shaped? | narrower and stiffer at base, wider at apex 25-35 mm |
| what is embedded in the tectorial membrane? | tips of OHC cilia |
| reticular lamina | -is ceiling of organ of corti -separates endolymph from cortilymph (similar to perilymph) -cilia penetrate the reticular lamina so they can bathe in endolymph (the rest of the hair cell bathes in perilymph) |
| OHCs are best for hearing________ | less intense sounds |
| IHCs are best for hearing ____________ | louder (more intense) sounds |
| How many rows of hair cells are there? | 3-5 rows OHCs 1 row IHCs |
| How many hair cells are there? | 12,000 OHCs 3500 IHCs |
| How are hair cells shaped? | OHC=test-tube shaped IHC=flask-shaped |
| what is the electrical charge of hair cells? | OHCs= -60 mV IHCs= -40 mV |
| are IHC stereocilia embedded in the tectorial membrane? | no, only OHC stereocilia are embedded |
| 5% of all auditory nerve fibers serve the | OHCs |
| 95% of all auditory nerve fibers serve the | IHCs |
| the cell bodies of the OHC and IHC neurons comprise the ______________ | spiral ganglion of the primary auditory neuron |
| the IHCs have less__________connectivity | efferent |
| efferent fibers emanating from superior olivary complex in brainstem= | olivo-cochlear bundle |
| what is the electrical charge of endolymph? | +80 mV (high potassium) |
| what is the electrical charge of perilymph? | low potassim |
| vestibular (endolymphatic) aqueduct | -contains endolymph -from vestibule to endolymphatic sac -helps regulate endolymphatic pressure to over or under-absorb endolymph |
| cochlear aqueduct | -contains perilymph from basal cochlea (scala tympani) to subarachnoid space -allows transfer of CSF |
| what is non-patent by age 50 in 50% of people? | cochlear acqueduct |
| scala vestibuli and scala tympani are filled with__________ | perilymph |
| scala media is filled with__________ | endolymph |
| organ of corti is filled with__________ | cortilymph (like perilymph) |
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