inner ear Flashcards
1
Q
3 parts of the cochlea
A
- scala vestiboli
- scala media
- scala tympani
2
Q
labyrinth
A
within the bony walls of the cochlea, complex network of delicate membranes
-connecting pathways in the petrous portion of the temporal bone
3
Q
transduction
A
converting acoustical-mechanical energy into electro-chemical energy
4
Q
cochlear functions
A
-transduction and frequency analysis
5
Q
frequency analysis
A
breaking sounds up into its component freqencies
6
Q
vestibule
A
- middle ear connects with the inner ear through the oval window
- behind the oval window is the vestibule
- leads to the hearing part of the ear, cochlea
7
Q
general anatomy of inner ear
A
- tube-shaped and separated into 3 sections by thin membranes
- from the beginning of the cochlea at the base to the apex at the outer end, the tube curves several time around the modiolus
8
Q
modiolus
A
bony center of the cochlea
9
Q
scala
A
the cochlea is separated ito 3 portions or ….
10
Q
reissner’s membrane
A
separates the scala vestibule from the scala media
11
Q
scala vestibuli is filled with what kind of fluid?
A
perilymph
12
Q
scala media is filled with what?
A
endolymph
13
Q
what does the basilar membrane spirit?
A
scala media and scala tympani
14
Q
what is the scala tympani filled with?
A
perilymph
15
Q
helicotrema
A
small opening at the apical end of the cochlea
-forms connection b/w the scala tympani and scala vestibuli
16
Q
stria vascularis
A
contributes to cochlear function, forms the lateral border of the scala media
- recieves generous supply of blood and has high rate of metabolism
- serves as a pump for the transporting K+ into endolymph, the cochlear fluid within the scala media
- plays crucial role in producing energy used by other structures- outer hair cells
17
Q
endocochlear potential
A
sizeable positive electrical charge within the scala media in comparison to the electrical state in other portions of the cochlea
18
Q
basilar membrane
A
narrow at the base and wider at the apex
-each movement of the stapes footplate produces vibration of the BM that travels away from the footplate
19
Q
base of the BM
A
narrow
stiffer
high frequencies
20
Q
apex of the BM
A
wider
looser
lower frequencies
21
Q
Traveling wave theory
A
- Bekesy studied it on cadavers
1. response always begins at the base
2. amplitude grows as it travels apically
3. reaches a peak at a point determined by frequency of the sound
4. vibration then dies out rapidly - pressure difference across the basilar membrane
22
Q
tonotopical organization
A
organization of the cochlea
-processing of sounds of diff freq at different locations along the membrane
23
Q
perilymph concentrations
A
high concentrations of Na and low concentrations of K
- very similar to cerebrospinal fluid
- similar to the inside of the Organ of Corti
24
Q
endolymph concentrations
A
high concentrations of K and low concentrations of Na
-significantly more positive than perilymph
25
cochlear fluids
the difference or gradient in ion composition and concentration of endolymph versus perilymph serves as an inner ear battery, supplying power for cochlear functions
-electrochemical potential difference in the cochlea is critical for powering the ongoing active processes within the cochlea
26
organ of corti
a complex of structures located on the BM
plays a critical role in hearing
rods and pilots form the main supporting framework and enclose the tunnel of Corti
-superior border= tectorial membrane
-contains cortilymph
27
inner hair cells
shaped like goblet or flask
- contain nucleus toward the center and mitochondria scattered throughout the cell
- stereocilia are in a single row and are not imbedded in the tectorial membrane
28
outer hair cells
shaped like cylinder or tube
contains nucleus near the base
mitocondria are arranged along the walls
stereo cilia are imbedded in the tectorial membrane
-stereocilia are arranged in 3 or 4 rows
29
movement of stereocilia
plays important role in converting mechanical energy from sound vibrations into chemical and electrical energy within hair cells
30
outer hair cell motility
vibrations of the BM activates the OHC
- movement of OHC is enhanced because the tops of tallest stereocilia are imbedded in tectorial membrane
- when activated the OHC alternatively become longer and skinner and then shorter and fatter
- rapid up and down movement
- contributes to movement of the BM and normal hearing
31
prestin
specialized motor protein
| rapid elongation and shortening is the underlying reason for motility of the OHC
32
otoacoustic emissions
what causes the cochlea's sensitivity and freq tuning at low and moderate intensities
33
recruitment
what happens in patients with sensory neural hearing loss
| -rapid growth of loudness
34
OHC difference
the energy supplied by the OHC motility helps overcome the loss of energy that occurs as the BM moves within the thick cochlear fluids
OHC motility improves our hearing sensitivity by 40-50 dB and contributes to our ability to distinguish freq
35
IHC difference
additional energy in the cochlea associated with OHC motility adds to vibration of the BM and increases activation of the IHC
-we cannot hear with our OHC alone, IHC function is essential - sends the info to the brain
36
efferent fibers
brain to the cochlea
37
afferent fibers
cochlea to the brain
38
VIII consists of....
type 1 and type 2 fibers
39
type 1 fibers of VIII
large and myelinated
make up 95% of the nerve
innervate the IHCs
40
type 2 fibers of the VIII
small myelinated and unmyelinated
| innervate with the OHCs
41
afferent neural pathways
carry info from the ear to the brain and in a rostal direction through the brain
- 95% communicate directly with the IHCs
- only 5% make connections with the OHCs
42
efferent system auditory system
descending pathways
- runs downward from the brain into the ear
- final portion of this system consists of nerve fibers originating in the lowest region of the brain that travel downward through the internal auditory canal to the cochlea
43
efferent innervation of the OHC
inhibitory
| -reduces the afferent activity caused by hair cell stimulation
44
crossed olivocochlear bundle
innervates the OHCs
45
uncrossed olivocochlear bundle
innervates the IHCs
| activation is controlled by the cortical activity and assists in detection of a signal within background noise
46
what is hearing dependent on?
transmission of electrical activity from the inner hair cells to the auditory nerve
-hair cells communicate with nerve fibers through a synapse which is defined as a "point of contact:
47
auditory neuropathy
disruption in the transmission of information from inner hair cells to and along nerve fibers results neural auditory dysfunction
48
eighth cranial nerve
transmits auditory and vestibular info from the ear to the brain
-almost all fibers connect via synapse with the IHCs
10-20 afferent fibers synapse with a single hair cell
-enclosed in a narrow passageway in the temporal bone called the internal audiotory canal
49
efferent auditory pathway
important for auditory function
| -extends downward within the internal auditory canal from the lower region of the brain to cochlear hair cells
50
internal auditory artery
blood supply to the cochlea after it branches off larger blood vessels near the brain
-important for auditory function
51
auditory nerves
bipolar and consist of a cell body with 2 axons projecting from the cell body in opposite directions
52
spiral ganglion
collection of auditory nerve cell bodies
53
Rosenthal's canal
passageway within the temporal bone that fibers travel medially into the modiolus
54
habenulae perforata
nerve fibers exit through small openings in the osseous spiral lamina
55
radial fibers
type 1 auditory nerve fibers
| -innervate the IHCs
56
characteristic frequency
activation is the greatest and the auditory nerve fiber is activated with the lowest sound intensity
57
frequency selectivity
responsiveness of auditory neurons to sounds at specific frequencies and not for sounds at other frequencies
58
coding of intensity
intensity of sound is partially represented as the number of spikes per second for nerve fibers
-firing rate increases only over a range of 20-50 dB of sound intensity
59
structures of the auditory brainstem
cochlear nuclei
superior olivary complex
lateral lemniscus
inferior colliculus
60
cerebellopontine angle
fibers from the right ear and the left ear enter into the brainstem at the junction of the medulla and the pons on each side of the brainstem
61
peripheral portion
outer, middle and inner ear
62
central portion
auditory nerve
brainstem
thalamus
auditory cortex
63
auditory afferent nuclei
```
8th nerve
cochlear nucleus
superior olivary complex
lateral lemniscus
inferior colliculus
medial geniculate body
auditory cortex
```
64
efferent auditory system
begins in the auditory cortex and includes pathways within each of the major auditory centers for the afferent system
-may be related to disorders like tinnitus
65
olivocochlear bundle
efferent fibers from the olivary complex in the brainstem that descend to the inner ear
66
medial OCB fibers
lead directly to the outer hair cells
67
lateral OCB fibers
indirect connections with inner hair cells
