Kady's Quizlet Flashcards
1
Q
Hyperpolarization
A
Neuron period of rest (refractory period)
Inside cell is more negative (less than -70 mV)
1
Q
superior/inferior
A
above/below
2
Q
standard anatomical position
A
standing upright
head faces forward
arms at sides
palms face forward
thumbs pointed outward
feet flat
toes pointed forward
3
Q
sagittal plane
A
divides body into left and right
4
Q
anterior/posterior
A
front/back
5
Q
coronal plane
A
divides into front and back
6
Q
What type of neurons are auditory neurons?
A
bipolar
7
Q
dorsal/ventral
A
dorsal = top of brain
ventral = bottom of brain
8
Q
voltage of resting membrane potential
A
-70 mV
9
Q
What are the steps of the action potential?
A
Depolarization, then hyperpolarization (resting period)
Gates open between Schwann cells at the Nodes of Ranvier
All or nothing event!
10
Q
perilymph
A
sodium-rich (Na+)
similar to CSF
located in scala vestibuli and scala tympani
11
Q
endolymphp
A
potassium-rich (K+)
produced by stria vascularis
in scala media (cochlear duct)
12
Q
What are the five balance organs?
A
Anterior/Superior SCC
Posterior SCC
Horizontal/Lateral SCC
Utricle
Saccule
13
Q
angular acceleration
A
semicircular canals
14
Q
linear acceleration
A
utricle and saccule
15
Q
Where does CN VIII insert?
A
pontomedullary junction
or
cerebellopontine angle
16
Q
What are the structures of the CNS?
A
brain
brainstem
cerebellum
spinal cord
17
Q
What are the structures of the PNS?
A
12 cranial nerves
31 spinal nerves
18
Q
What is the purpose of nerve cells?
A
Messenger between the nervous system and the body
19
Q
What are neurons?
A
nerve cells
20
Q
What do neurons do?
A
Transmit nerve impulses (send signals)
21
Q
What do neuroglia do?
A
support neurons
provide nutrients
22
Q
Name the parts of a neuron
A
Dendrites
Axon, myelinated
Cell body
23
Q
What’s the function of the dendrite?
A
Receive afferent signals
24
Where do axons originate?
axon hillock of the cell body
25
What is the function of the synapse?
Site where neurons communicate with other neurons, muscles, or glands
26
What is the function of myelin?
Supports, protects, and insulates axon
Increases conduction speed of electrical signals (fire faster)
27
Nodes of Ranvier
gaps in the myelin sheath of a nerve, between adjacent Schwann cells
site of ion gates
28
What is an internode of neuron?
Area of axon wrapped in myelin
Between Nodes of Ranvier
29
Nuclei
group of cell bodies in the CNS
30
ganglion
group of cell bodies in the PNS
31
What does the brainstem consist of?
Midbrain
Pons
Medulla oblongata
32
What is the purpose of the brainstem?
Connects the diencephalon to the spinal cord
Monitors all brain output
33
What is the tegmental area of the the medulla responsible for?
heartbeat
blood vessels
breathing
34
Where is the medulla located?
lowest portion of the brainstem
35
What is located in the pyramidal area of the medulla?
descending motor fibers
36
What does the pons contain?
cochlear nerve nuclei
reticular formation
direct contact to the cerebellum for vestibular
37
What is the function of the midbrain?
generates neurotransmitters
38
What are the important structures of the midbrain?
superior and inferior colliculi
39
What is the cerebellum's function?
-equilibrium and coordination
-muscle tone, speed, and range
-integration of motor and vestibular input
40
superior colliculus
vision
41
inferior colliculus
projections from ear to brain (ascending)
42
diencephalon
thalamus and hypothalamus
43
Where is the medial geniculate body located?
thalamus
44
What is the function of the basal ganglia?
regulates motor function
muscle tone
(ex: Parkinson's)
45
telencephalon
cerebral hemispheres
basal ganglia
corpus callosum
46
Which are the important Brodmann's areas?
Areas 41, 22, and 42
47
grey matter
superficial
unmyelinated cell bodies
48
white matter
deep
myelinated axons and dendrites
49
What is the purpose of sulci and gyri?
Increases surface area of the brain
50
sulci
grooves
51
gyri
ridges
52
fissures
deep grooves in the brain
53
What is the function of the corpus callosum?
connects left and right hemispheres
heavily myelinated
54
lateral/medial
away from midline / toward midline
55
contralateral / ipsilateral
opposite side / same side
56
bilateral/unilateral
both sides / one side
57
transient
temporary
58
persistent
lasting
59
static
unchanging
60
improving
beginning to resolve
61
progressive
continue to worsen
62
acute
over minutes or hours
63
subacute
over days or weeks
64
chronic
over months or years
65
bipolar nerve cell
one dendrite
one axon
auditory nerve (IHC and OHC)
66
multipolar nerve cell
many dendrites
one axon
CNS to save space
67
unipolar nerve cell
combination one dendrite/one axon
68
Type I afferent neurons
heavily myelinated
1:1 ratio on IHC (exclusive relationship)
69
Type II afferent neurons
innervate multiple OHCs
70
neuroglial cells
physical support
insulation
nutrients for neurons
NOT PART OF ACTION POTENTIAL
71
Schwann cells
myelinate axons in the PNS
72
oligodendroglial cell
myelin in CNS
73
endoneurium
perineurium
epineurium
layers of connective tissue of a nerve from inferior to exterior
74
Voltage change required for an action potential
15 mV
75
depolarization
Na (endolymph) enters the cell
Cell becomes more positive (-55 mV or higher)
76
congenital age
beginning at conception
77
gestational age
beginning at start of last menstrual cycle
78
morphogenesis
development of an organism and its structures
79
How is morphogenesis achieved?
sparked by gene expression and cell fate determination
80
How does CNS development begin?
trilaminarization
81
What is derived from ectoderm?
skin
nervous system
sense organs
82
What is derived from mesoderm?
skeleton
circulatory system
kidneys
reproductive system
muscles
83
Embryology:
Weeks 1 and 2
egg is fertilized and divides (blastula)
84
Embryology:
Day 21
neural groove invaginates toward the notochord
85
Embryology: Day 22
neural tube closure begins
otic placode forms
86
Embryology: Day 24
neural tube continues to close
otic placode begins to invaginate
87
Embryology: Day 25
neural tube is fully closed
88
Anencephaly and Spina Bifida
Neural tube malformation
Missing brain or incomplete closure of spinal cord
Reduced by folic acid supplement
Revealed through ultrasound
89
Embryology: Day 27
otic pit forms
90
When are teratogens most harmful?
weeks 4-9
91
Which end of the neural tube is the brain?
rostral
92
What is the prosencephalon?
forebrain
93
What does the prosencephalon divide into?
telencephalon and diencephalon
94
What does the mesencephalon develop into?
midbrain
95
What ist he rhomencephalon?
hindbran
96
What does the rhombencephalon divide into?
metencephalon and myelencephalon
97
What does the metencephalon become?
pons and cerebellum
98
What does the myelencephalon become?
medulla oblongata
99
Embryology: Week 4
-rostral neural tube divides
-cranial nerve nuclei present (in BAs)
-otic vesicle formed
-"hollow" cochlear duct formed
-branchial arches present
-pharyngeal pouch extends
-primordial ossicles present
100
Pathology:
Halted cochlear development at Week 4
Common cavity
101
Pathology:
Malformation of branchial arches I and II
Treacher Collins Syndrome
(inner ear generally unaffected)
102
Embryology: Week 5
branchial groove I deepens (beginning of EAM)
103
Embryology: Week 6
-SCC arch-like formations visible
-rudimentary utricle and saccule formed
-ET form from pharyngeal pouch
-tympanic cavity forms (endoderm)
-hillocks of pinna form (BA 1 and 2)
104
Embryology: Week 7
cochlea has one coil
105
Embryology: Week 6.5
cochlea begins coiling
SCC is more defined
106
Pathology:
Halted cochlear development at Week 6
cochlear hypoplasia
107
Pathology:
Halted cochlear development at Week 7
Incomplete partition/Mondini's dysplasia
May not affect hearing ability
108
Auricle movement: Weeks 7-20
superior and lateral movement as face and jaw displaces it
109
Pathology:
Atypical movement of pinna
Caudal displacement
Goldenhar Syndrome
110
Embryology: Week 8
EAM sinks toward tympanic cavity with thick epithelium (metal plug)
Mesoderm grows between EAM and tympanic cavity
111
Pathology:
Halted cochlear development at Week 9
"Normal" structural development, missing internal structures
112
Embryology: Week 9
Tympanic membrane is forming
113
Embryology: Weeks 8.5 - 10
incus and malleus complete but still cartilaginous
114
Embryology: Week 10
-corpus callosom present
-Organ of Corti begins development (3 ducts in cochlea)
-tectorial membrane defined
115
Pathology: Agenesis
failure of all or part of an organ to develop
under-developed corpus callosum; risk for APD
116
Embryology: Week 11
hair cells begin developing
117
How do hair cells develop?
inner before outer
base to apex
afferent before efferent
118
Embryology: Week 12
afferent nerves on ALL hair cells
stereocilia begin to develop
119
Embryology: Week 14
all stereocilia present (not adult-like)
120
Embryology: Week 15
stapes formation is complete but still cartilaginous
121
Embryology: Week 16
ossification of incus and malleus begins
122
When is the auricle essentially adult-like?
16-20 weeks (grows until 9 years old)
123
Embryology: Week 18
ossification of stapes begins
124
Embryology: Week 19
three layers of tympanic membrane is complete
125
When is the stapes completely ossified?
adulthood
126
Embryology: Week 20
-cerebral hemispheres are smooth
-cochlea and vestibular organs are essentially complete
-efferent replace afferent on OHCs
127
Embryology: Week 22
stereocilia adult-like shapes
128
Embryology: Week 24
sulci and gyri begin to form
cochlea is fully developed (definition of OoC)
129
Embryology: Week 26
malleus and incus are completely ossified
130
When is the EAM completely open?
week 28-30
131
Embryology: Week 30
cochlear development complete (adult-like hearing)
132
hydrocephalus
excessive CSF in the brain
133
microcephaly
significantly reduced skull/brain
134
Which deformities go together?
outer and middle ear
135
What is the cochlea derived from?
ectoderm
136
What is the lining of the middle ear derived from?
endoderm
137
Can a fetus hear at 20 weeks GA?
Yes, but with elevated thresholds and poor discrimination
138
When can electrophysiologic measures be estimated for a fetus?
30 weeks
139
What is formed from branchial arch I?
malleus
part of incud
tragus
tensor tympani
140
What is formed from branchial arch II?
part of incus
stapes
stapedius muscle
141
What is the tympanic cavity formed from?
pharyngeal pouch
142
What invaginates to become the EAM?
branchial arch I
143
What are the hillocks derived from?
branchial arch I and II
144
What are the ossicles derived from?
mesoderm
145
What is the lateral layer of the tympanic membrane?
ectoderm
146
Pinna strucures
lobe
cavum concha
cymba concha
antitragus
intetragal notch
antihelix
helix
scaphoid fossa
triangular fossa
crus of antihelix
crus of helix
147
Name 3 extrinsic auricular muscles
superior
anterior
posterior
148
Are there intrinsic muscles in the pinna?
Yes, 6 of them but underdeveloped in humans (wiggle ears)
149
Upper pinna nerve supply
auriculotemporal nerve - branch of trigeminal nerve
150
Lower pinna nerve supply
greater auricular nerve - branch of C2 and C3 spinal nerves
151
Which cranial nerve supplies the outer ear?
CN VI, VII, IX, X, and Spinal C2 and C3
152
What does the posterior auricular (carotid) artery supply?
posterior surface, lobe, concha
153
What does the superficial temporal (carotid) artery supply?
upper pinna
154
What is the pinna made of?
elastic cartilage and ligaments
thin epidermis
no subcutaneous fat
155
Why is the pinna very susceptible to trauma?
no subcutaneous fat
156
Resonance of the concha
8 dB with boot at 5000 Hz
157
Size of the concha
~1-2 cm
158
What is the purpose of the pinna?
sound scoop
8 dB boost at 5000 Hz
localization via ILD and ITD
159
Typical extension of pinna from skull
15-30 degrees
160
What is a pre-auricular appendage?
Improper migration of cartilage in front of tragus
may indicate syndrome
161
Pathology:
Pre-auricular sinus
divot, may lead to nasopharynx
usually benign
162
Pathology:
Auricular Dysplasia
malformed pinna
"earbud"
possible EAM atresia
163
Pathology:
CHARGE syndrome
prominent pinna
164
Pathology:
Cup Ear
thick overlapping helix
may affect hearing aid fitting
165
Pathology:
Down Syndrome
cup ear
small EAM and cerumen buildup
chronic otitis media
CHL and SNHL
166
types of skin cells
epidermis
dermis
subcutis
167
Layers of epithelium
squamous
melanocyte
basal cell
168
Pathology:
Actinic Keratosis
pre-malignant growth occurs on sun-damaged skin
169
Pathology:
Squamous Cell Carcinoma
scaly patches
open sores
rarely fatal
170
Pathology:
Basal Cell Carcinoma
shiny and pink
not deadly; but disfiguring
171
Pathology:
Melanoma
serious skin cancer
black and uneven
172
Pathology:
Hairy Pinna Syndrome
affects resonance, cerumen removal, and hearing aid fitting
173
Tympanic Membrane Structures
pars flaccida
pars tensa
annular ligament
cone of light
umbo
manubrium
short/lateral process of malleus
long process of incus
chord tympani
posterior fold
anterior fold
174
What does the annular ligament do?
holds TM to canal wall
175
Why does the pars tensa have more rigidity?
third layer of connective tissue
176
Where does the manubrium face?
anterior, superior quadrant
177
Where is the cone of light?
anterior, inferior quadrant
178
Where are the TM perforations typically?
posterior, inferior quadrant
179
What are the four TM quadrants?
anterior superior
anterior inferior
posterior superior
posterior inferior
180
Is the TM concave or convex?
concave
181
What are the measurements of the TM?
8-9 mm horizontally
9-10 mm vertically
0.1 mm thick
182
What are the three layers of the TM?
epidermal (lateral)
fibrous tissue (middle)
mucosal lining (medial)
183
What is Shrapnell's membrane?
pars flaccida
184
What is the function of the TM?
transform acoustic energy to mechanical energy
185
Pathology:
Tympanosclerosis
scarring on TM
186
Pathology:
Tympanic perforation
CHL
dry or wet
187
Pathology:
TM refraction
negative pressure due to ET dysfunction
188
Pathology:
Cholesteatoma
-collection of dead skin cells within the middle ear
-stimulates osteoclasts
-seen in pars flaccida
-CHL, facial paralysis, vertigo
189
What is the function of a PE tube?
relieve ET dysfunction
aerate middle ear space
190
What is the lining of the EAM?
squamous epithelium
191
What are the measurements of the EAM?
2.5 - 3 cm length
.75 cm diameter
192
What is the outer 1/3 of the EAM made of?
carilaginous
0.5 - 1.0 mm skin
cerumenous glands
dynamic variability when moving mandible
tympanomandibular joint
193
What is the inner 2/3 of EAM made of?
bony
0.2 mm skin
profuse blood supply
fixed diameter
ossification by 3 years old
194
Narrowest part of EAM
osseocartilaginous junction (isthmus)
landmark for ear mold impressions
195
Anterior Wall and Roof of EAM nerve supply
auriculotemporal nerve - branch of trigeminal nerve
196
Posterior Wall and Floor of EAM nerve supply
auricular nerve - branch of vagus nerve
197
What does Arnold's branch of CN X do?
cough reflex in EAM
198
Which walls of the EAM are most sensitive?
posterior and floor
199
What is the function of the EAM?
amplify 2000-4000 Hz by 10-15 dB
peak resonance at 2700 Hz by 17-22 dB
filter low frequencies
protect TM by cerumen, hair, and distance
200
Where is cerumen produced?
outer 1/3 of EAM
201
What is the purpose of cerumen?
antibiotic/antifungal
anti-insect
catch foreign bodies
lubricant
202
sebaceous glands
sebum: oily substance for lubrication
close to hair follicles
203
ceruminous glands
wax-like substance
apocrine sweat
204
Causes of cerumen impaction
overactive ceruminous glands
lack of epithelial migration
pushing of cerumen medially
205
Epithelial migration
centrifugal migration from umbo
0.5-1.0 mm per day
206
Pathology:
Keratosis Obturans
obstructing desquamated epithelium
abnormal epithelial migration
207
Pathology:
Osteoma
single bony growth
208
Pathology:
Exostoses
multiple bony growths
common in cold water swimmers
209
Pathology:
Microtia / Anotia
small / missing pinna
210
Pathology:
Otomycosis
fungal infection
hard to treat
211
Pathology:
External Otitis
Swimmers ear
infection of EAM
painful to touch
212
Pathology:
Malignant Otitis Externa
high morbidity rate
primarily in diabetes mellitus
213
What is the middle ear cavity?
air filled cavity in petrous temporal bone
214
Roof of the middle ear cavity called?
tegmental wall
215
Floor of the middle ear cavity called?
jugular wall
216
Anterior wall of the middle ear cavity
carotid wall
217
Posterior wall of middle ear cavity
mastoid wall
218
Medial wall of middle ear cavity
labyrinthine wall
219
Lateral wall of the middle ear cavity
membranous wall
220
Tegman Tympani
thin plate of bone separating the middle ear from the cranial cavity
221
Anterior wall of ME cavity structures
tensor tympani
Eustachian tube to nasopharynx
222
Posterior wall of ME cavity structures
auditus ad antrum = opening to mastoid air cells
sigmoid sinus
pyramidal eminence
stapedius muscle
223
Which cranial nerves run through the jugular fossa
CN IX, X, XI
224
What is the purpose of the ossicles?
impedance matching and pressure equalization
225
What are the components of impedance matching?
areal ratio (large TM to small oval window) : 17 dB
buckling of TM : 6 dB
lever action of ossicles: 2 dB
226
What does the stapes move?
oval window of vestibule
moves perilymph
227
Epitympanic Recess
superior portion of middle ear (above TM)
228
Tympanic Cavity Proper
space directly medial to tympanic membrane
229
Lateral wall of ME cavity structures
bony wall superiorly
tympanic membrane (3 layers)
handle of malleus firmly attached
230
Radial Fibers of TM
collagen
superficial
231
Circular Fibers of TM
thicker on periphery
deep
232
Medial wall of ME cavity structures
longitudinal ridge (CN VII)
prominence of lateral SCC
cochleariform process
oval window
round window
promontory
233
What is the promontory?
bony accommodation for the basal turn of the cochlea
234
What holds the stapes to the oval window?
annular ligament
235
Describe the movement of the stapes
like a door hinge
anterior moves more than posterior
236
Pathology:
Otosclerosis
bony growth of annular ligament
stapes cannot move = CHL
237
Where does the tensor tympani connect?
neck of the malleus
238
Which nerve innervates the tensory tympani?
trigeminal nerve
239
What is the chorda tympani?
branch of facial nerve
sense of taste
within ME cavity
240
ME cavity measurements
~2.4 mm width
~13 mm vertical
~2-3 cm volume
241
Which cranial neve innervates the stapedius muscle?
CN VII, facial
242
What connects the stapedius to the stapes?
stapedial tendon
243
Which artery lies next to the anterior wall of the middle ear cavity?
internal carotid artery
244
What is the groove along the floor of the ME cavity?
jugular fossa
245
What is the space between the malleus and the TM?
Prussia's space
246
Where does the stapedial tendon attach to the stapes?
posterior crus
247
Which direction does the stapedius muscle pull?
lateral and posterior
248
Which direction does the tensory tympani pull?
medial and anterior
249
Measurements of the Malleus
23-37 mg
9 mm long
250
Measurements of Incus
23-32 mg
5x7 mm
251
Measurements of Stapes
2.1-4.3 mg
2.5-3.8 mm
Footplate: 1.4 x 3.2 mm
252
Measurements of Tensor Tympani
25 mm long
5.8 mm cross section
253
What occurs during tensor tympani and stapedius muscle contraction?
response to loud sounds
lock ossicles
retract TM
40 ms response time
dampens sound intensity (20 dB in low freq)
contraction increases as intensity increases
congruent!
254
Measurements of Stapedius Muscle
6.3 mm long
4.9 mm cross section
255
Ipsilateral Acoustic Reflex Testing
stimulating and recording in the same ear
256
Contralateral Acoustic Reflex Testing
stimulus in one ear, record in the other ear
257
What is the function of the Eustachian Tube?
air pressure equalization
drainage to nasopharynx
258
What is the "direction" of the ET?
45 degrees inferior, anterior, and medial
259
Measurements of Eustachian Tube
3.5 - 3.9 mm long
narrowest at isthmus
260
Which muscles opens the ET?
tensor veli palatini
261
Pathology:
Eustachian Tube Dysfunction
oxygen in ME is absorbed by the mucosal lining
reserve air from mastoid air cels
serous fluid builds up
TM retracts
262
Treatment - Serous Otitis Media
nothing
PE tube
myringotomy
263
Treatment - Supportive Otitis Media
antibiotics
PE tube
myringotomyWh
264
What is the sense organ for hearing?
cochlea
265
4 main parts of temporal bone
squamous
mastoid
petrous
tympanic
266
What is a temporal bone slide?
thin slice of temporal bone
structures vary based on depth of cut
267
Where are the cochlea and vestibular organs located?
petrous portion of temporal bone
268
Bony Labyrinth
portion of the temporal bone
houses membranous labyrinth
hardest bone in the body
269
Membranous Labyrinth
fluids and sensory organs for hearing and balance
cochlea
utricle
saccule
SCCs
270
Measurements of Cochlea
~5 mm tall
~1 cm wide
2.2 - 2.9 turns
wider and flatter towards apex
271
canalis reuniens
transports fluids from cochlea to saccule
272
Fluid in the vestibule
perilymph (Na+)
273
Fluid in scala media
endolymph (K+)
274
fluid in scala vestibuli and scala tympani
perilymph (Na+)
275
Place where the scala vestibuli and scala tympani meet
helicotrema
276
Core of the cochlea
modiolus
277
Purpose of Modiolus
houses nerves and blood vessels
278
Characteristics of basilar membrane at base
narrow
stiff
high frequency sensitive
279
Characteristics of basilar membrane at apex
wide
loose
low frequency sensitive
280
osseous spiral lamina
bony shelf for auditory nerve fibers
not flexible
281
habenula perforata
exits for nerve fibers out of osseous spiral lamina
282
spiral ligament
supportive connective tissue
283
stria vascularis
produces endolymph in scala media
284
spiral ganglion
auditory nerve cell bodies
285
limbus
attachment for Reissner's membrane and tectorial membrane
286
Organ of Corti Anatomy
Reissner's membrane
basilar membrane
tectorial membrane
limbus
stria vascularis
spiral ligament
IHCs
OHCs
support cells
cortilymph (between support cells)
287
Length of Basilar Membrane
25-35 mm
288
Tectorial Membrane
gelatinous flap above OoC
articulates with tallest stereocilia of OHC
increase in mass and width from base to apex (like BM)
289
Types of Supporting Cells in the Cochlea
Dexter's cells
Henson's cells
Claudius cells
Boetcher's cells
290
What is the function of sensory cells?
transduce mechanical energy to electrochemical energy for the nervous system
291
OHC characteristics
12,000
3-5 rows
"tube" shaped
mostly efferent (motor) with many connections
sits on Deiter's cells
"W" shaped
60-160 stereocilia
292
IHC characteristics
3500
1 row
"flask" shaped
mostly afferent (sensory)
exclusive relationship
"U" shaped
50-70 stereocilia
293
Stereocilia characteristics
tip-links (row to row)
cross-links (same size to same size)
ion channels
294
"Surface" that stereocilia poke through
reticular lamina
295
How do ototoxic drugs damage hearing?
usually take out OHC before IHC
cannot be regrown
296
How does loud music damage hearing?
displaces hair cells
temporary or permanent
297
Afferent nerve fiber pathway
from hair cell to brainstem via CN VIII
298
Efferent nerve fiber pathway
from brainstem to hair cells via CN VIII
primarily terminates on OHC
299
Type I afferent nerve fibers
95% auditory nerve fibers
terminate on each IHC (exclusive relationship)
each IHC has ~20 nerve fibers
300
Type II afferent nerve fibers
5% of auditory nerve fibers
one fiber on many OHC
301
How does a traveling wave affect the basilar membrane?
pressure wave from stapes causes pressure difference in scala vestibuli and scala tympani, causes vertical displacement along BM in the scala media
302
How does the stapes pushing inward affect the BM?
causes condensation
pushes BM downward
stereocilia shearing down
ion channels closed
inhibitory
303
How does the stapes pulling outward affect the BM?
causes refraction
pulls BM upward
stereocilia shearing up
ion channels open = K rush in (endolymph)
excitatory
304
How is frequency represented by the stapes?
faithful representation
linear displacement of 1:1 ratio
305
How is intensity represented by the stapes?
pushes into vestibule shallower/deeper is quiet/loud
306
Which movement excited the hair cells?
towards the tallest stereocilia
307
What causes upward spread of masking?
stimulating unintended areas of the BM by increasing the intensity of sounds
causes less frequency selectivity
308
Why is the cochlea nonlinear
to give us a greater dynamic range!
cochlear compression (reduce impact of loud sounds)
cochlear amplifier (OHCs amplify soft sounds to stimulate IHCs)
309
Describe the cochlear amplifier
move tectorial membrane
increase amplitude of the signal
increased total displacement of BM
310
Where is the cochlear amplifier more useful?
up to 50 dB (OHC hearing range)
311
What is the measurement of the cochlear amplifer called?
otoacoustic emissions
312
What are the types of OAEs?
spontaneous (SOAE)
transient evoked (TEOAEs)
distorted produce (DPOAE)
313
What happens when the IHCs are depolarized?
release neurotransmitters at synaptic cleft
excite auditory nerve fibers
314
What happens when the IHCs are hyperpolarized?
decrease neurotransmitters at the synaptic cleft
inhibits auditory nerve fiber firing
315
Explain the resonance of the BM
tonotopically mapped
traveling wave amplitude builds up resonance point then quickly attenuates
316
Describe the tonotopicity of CN VIII
high frequencies outside
mid frequencies inner
low frequencies in the center
317
What is the characteristic frequency?
where it takes the least energy to stimulate the auditory nerve
318
How does OHC health affect tuning curves?
affects their sharpness/frequency specificity
319
What are the two types of frequency coding?
Place coding: location of stimulation
Temporal coding: firing rate after 1000 Hz relies on volley principle
320
How is intensity coded by the auditory nerve?
number of fibers involved and higher firing rate
321
What does reflex decay measure?
recovery speech of the nerve fibers
louder = more fibers = change in recovery time before firing again
evidence of retrocochlear pathology
322
Where does the auditory nerve exit through?
IAM
323
Which nerves are in the internal auditory canal (IAC)?
3 branches of CN VIII
CN VII
324
How does the location of a vestibular schwannoma affect the presentation of symptoms?
depends on if it is touching facial, vestibular, auditory, or a combination
325
What is hearing?
perceptual representation of acoustic energy
326
What acoustic features are coded by the CNS?
frequency
temporal issues
intensity
binaural cues
327
Describe the ascending central auditory pathway from the cochlea
cochlea
cochlear nucleus
superior olivary complex
nucleus of the lateral lemniscus
inferior colliculus
medial genicular body (thalamus)
auditory cortex
328
How many cochlear nuclei are there?
two
329
Which structure is the first level where sound is processed?
cochlear nucleus
330
How are acoustic features enhanced within the neural signal?
neural firing
331
What are the three major divisions of the cochlear nucleus?
posterior ventral
anterior ventral
dorsal
332
Where is the cochlear nucleus located
pontomeduallary junction or cerebellopontine angle
333
How is the cochlear nucleus tonotopically organized?
low frequencies ventral
high frequencies dorsal
334
Characteristics of the anterior central cochlear nucleus
localization
large synapse with auditory nerve fibers
periodicity
entire frequency range
335
Characteristics of the posterior central cochlear nucleus
stimulus onset
enhances temporal cues
336
Characteristics of dorsal cochlear nucleus
duration coding
"build up" from onset
localization
337
Where do the auditory nerve fibers go after leaving the cochlear nucleus?
20% ipsilateral SOC
80% contralateral SOC
338
What is the function of IPSI and CONTRA auditory nerve fibers?
binaural hearing (temporal, intensity, squelch, dual input)
binaural processing
339
Where is the SOC located?
pons
340
Where is the first level of binaural integration?
SOC
341
What is the function of the SOC?
process binaural input of ILD and ITD (localization, fusion, lateralization)
342
What is the nuclei of the SOC?
medial superior olive (MSO)
lateral superior olive (LSO)
trapezoid body
343
What is the primary function of the MSO?
intraural time difference
