Comd 3400 Exam Four

Front 1

Phalangeal processes come up higher on

Back 1

inner hair cells but not outer hair cells

Front 2

What are characteristics of the inner hair cell? (6)

Back 2

droplet shaped, cell body

cuticle

stereocilia

has no inner support

single row between inner phalangeal cell and inner rod of Corti

same inclination of the inner rod of Corti

Front 3

What are characteristics of inner hair cell stereocilia? (4)

Back 3

approx 48 cilia per inner hair cell

stiff, resilient

longer toward outside and toward apex of cochlea

2 rows parallel to axis of basilar membrane

Front 4

When are kinocilia present in the body?

Back 4

during embryonic development

disappear during the latter part of fetal life

the remaining structure is called a basal body

Front 5

How many inner hair cells per ear?

Back 5

3,500

Front 6

How many inner hair cells per mm are throughout the cochlea?

Back 6

80 per mm at the basal end

115 per mm at the apical end

Front 7

How many rows of inner and outer hair cells are there?

Back 7

one row of inner

three rows of outer

Front 8

Basal bodies are found in

Back 8

adult vestibular cells

Front 9

Which row of stereocilia is the longest?

Back 9

the outer row

Front 10

The cilia are joined by

Back 10

very fine fibrils so that all the cilia on one cell tend to move as one unit when the longest ones are bent

Front 11

Stereocilia are connected sideways by

Back 11

links which couple the stereocilia together mechanically

Front 12

A second set of stereocilia links are at the

Back 12

tips

Front 13

What happens when tip links are stretched?

Back 13

membrane channels open

Front 14

Cilia contain what type of protein?

Back 14

actin

which suggest they may be motile

Front 15

Hair cells are surrounded by

Back 15

plasma membrane

Front 16

What shape are outer hair cells?

Back 16

cylindrical

Front 17

How many rows of outer hair cells are there?

Back 17

3 rows near the base
4 rows in the middle
5 rows near the apex

Front 18

The body of an outer hair cell is

Back 18

shorter at the base of the cochlea
and
longer at the apex

Front 19

What shape do the outer hair cell rows make?

Back 19

either a "V" or "W" transverse to the axis of the cochlear duct

the base of the V or W points toward the spiral lamina

Front 20

Inner and outer hair cells respond to what kind of movement?

Back 20

lateral (radial) shearing movement

Front 21

How many outer hair cell cilia are there?

Back 21

130 cilia per cell at the base of the cochlea

70 cilia per cell at the apex

Front 22

How many outer hair cells per ear?

Back 22

about 13,500 per ear (lecture (CM19) and book)

(noted as 12,000 in another lecture; CM22)

Front 23

What is the general function of the cochlea?

Back 23

translate the mechanical stapes vibrations into neural responses in the auditory branch of the 8th nerve

dependent on basilar membrane properties

Front 24

The stapes does what on a compression?

Back 24

pushes inward

Front 25

During compression, what develops on both sides of the cochlear partition?

Back 25

a pressure gradient

Front 26

What happens to the basilar membrane during compression?

Back 26

deflected towards the scala tympani

Front 27

What happens at the round window during compression?

Back 27

fluid forces the round window membrane out

Front 28

Vibratory action of the stapes is what to the basilar membrane?

Back 28

coupled

Front 29

Due to cochlear mechanics, the helicotrema acts as if it is

Back 29

closed

Front 30

What is the function of the helicotrema?

Back 30

a static balance for perilymph

Front 31

The response of the basilar membrane to stimulus is what?

Back 31

a traveling wave

Front 32

When the basilar membrane is stimulated, it moves in what fashion?

Back 32

transverse or radial
and
longitudinal

Front 33

No matter where the stimulus begins in the cochlea, the wave will always travel from the base to the apex. What is this called?

Back 33

The Traveling Wave Paradox

Front 34

The slope of the envelope is less from the point of maximum displacement to the

Back 34

base of the cochlear duct

Front 35

What two principles account for the shearing mechanism associated with the cilia on the outer hair cells?

Back 35

changes in radii during compression and rarefaction

off set pivot points between the tectorial and basilar membranes

Front 36

When the basilar membrane is displaced downward, the cilia are bent to the

Back 36

left

Front 37

What is Pascal's principle?

Back 37

pressure at any point in a closed-fluid system is transmitted to all other points in the system

Front 38

Since perilymph is like water and the cochlear partition is like gelatin, this creates what between the two?

Back 38

an interface

Front 39

Low frequencies tend to mask

Back 39

high frequencies

(low frequencies activate all the segments extending from the basal end to whatever maximum point nearer to the apex)

Front 40

The basilar membrane has been likened to an

Back 40

acoustic filter with a shallow low-frequency rise and a very steep high-frequency cutoff

Front 41

Bekesy demonstrated that what cannot account for basilar membrane displacement?

Back 41

simple resonance

Front 42

The most unique property of the traveling wave is the

Back 42

location of its maximum

Front 43

The single most important property of the cochlear partition seems to be

Back 43

the gradual changes in stiffness from the base to the apex

Front 44

What are the four electrical potentials of the inner ear?
ACDS

Back 44

AP ⇒ Action Potential

CM ⇒ Cochlear Microphonics

DC ⇒ Direct Current Resting Potentials

SP ⇒ Summating Potential

Front 45

What are cochlear microphonics?

Back 45

AC responses to acoustic stimulation

mimics the incoming waveform stimulus

Front 46

Where are cochlear microphonics generated?

Back 46

at the cilia of the hair cells

Front 47

Cochlear microphonics represent

Back 47

the amplitude, frequency, and timing characteristics of acoustic input

Front 48

Cochlear microphonics can be measured where?

Back 48

along the entire basilar membrane for low frequencies

at the basal end for high frequencies

Front 49

What causes cochlear microphonics?

Back 49

radial bending or shearing of the hair cell stereocilia

Front 50

When is the cochlear microphonic potential no longer present?

Back 50

when the cochlear hair cells are destroyed

Front 51

Cochlear microphonics are highly dependent on

Back 51

blood supply to the inner ear

Front 52

What is the Summating Potential?

Back 52

a DC electrical response that follows the envelope pattern of the acoustic wave

a shift in the baseline of the cochlear microphonic usually in the negative direction but can be positive

Front 53

What intensity is required to measure the summating potential?

Back 53

20-30 dB more compared to measuring the cochlear microphonic

Front 54

The sensitivity of the cochlear microphonic is greater than the sensitivity of the

Back 54

summating potential

Front 55

What causes the summating potential?

Back 55

longitudinal bending or shearing of the inner hair cells in the direction of the length of the cochlear partition

Front 56

Summating potentials are

Back 56

a composite of a number of bioelectric components

Front 57

What are the two resting potentials?

Back 57

intracellular polarization

endolymphatic (endocochlear) potential

Front 58

Resting potential is

Back 58

the normal DC charge of an unstimulated area

(resting potentials exist without acoustic stimulation)

Front 59

Intracellular polarization is

Back 59

a negative 80 mV charge present in most body tissues, including hair cells and cortilymph

Front 60

What is endolymphatic potential?

Back 60

positive polarization of 80 mV unique to the endolymph of the scala media

Front 61

What is responsible for the positive resting potential of endolymph?

Back 61

stria vascularis

Front 62

What is DC Fall?

Back 62

endolymphatic potential decreases as long as the stimulus persists

same as summating potential

Front 63

The action potential is usually considered as the

Back 63

discharge pattern, or the over-all action pattern, of the entire cochlear portion of the 8th nerve

Front 64

What is an action potential?

Back 64

a short sudden change in charge which moves a constant amplitude along the length of the nerve

Front 65

An action potential obeys the all-or-none law which means

Back 65

the nerve either fires at its maximum limit or not at all

Front 66

8th nerve fibers demonstrate

Back 66

absolute and refractory periods

Front 67

When single unit action potentials are measured, the response from the nerve fiber is called a

Back 67

spike

Front 68

Spikes occur in what kind of pattern when the electro-chemical status of the neuron is ready to fire?

Back 68

irregular

Front 69

For action potentials, when a timed stimulus is presented spikes occur at what interval?

Back 69

regular interval corresponding to the pattern of the click

Front 70

1st order neurons are

Back 70

associated with the hair cells and have projections to the dorsal and ventral cochlear nuclei, where they terminate

they are at the level of the spiral ganglion

Front 71

1st order neurons collectively are known as the

Back 71

spiral ganglion

Front 72

What is the Canal of Rosenthal?

Back 72

a canal following the course of the bony spiral lamina of the cochlea around the modiolus which contains the spiral ganglion.

Front 73

The 1st order neuron has peripheral dendritic extensions that attach where?

Back 73

the base of a hair cell

Front 74

The 1st order neuron has central axonal extensions that terminate where?

Back 74

either at the dorsal or ventral cochlear nuclei

Front 75

How do nerve fibers descend from the apex of the cochlea?

Back 75

through the middle of the modiolus and out the foramen centrale

apical fibers constitute the core of the 8th nerve, which represents low frequencies

Front 76

How do nerve fibers descend from the base of the cochlea?

Back 76

down the periphery of the modiolus and out the tractus spiralis foramina

basal fibers constitute the periphery of the 8th nerve, which represents high frequencies

Front 77

Why is the 8th nerve trunk twisted?

Back 77

the nerve develops before the cochlea, therefore as the cochlea develops in fetal life the nerve twists along with the growth of the structure

Front 78

The internal auditory meatus enters the brainstem where?

Back 78

medulla oblongata, laterally at the level of the lower pons

Front 79

What does the internal auditory meatus contain?

Back 79

the entire 8th nerve

two branches of the vestibular nerve enter the meatus to meet the auditory portion and then combine into the 8th nerve

Front 80

Neurons of the ascending auditory pathway end at the

Back 80

auditory cortex at the Sylvian fissure
(fissure of Sylvias)

Front 81

The ascending auditory pathways are more contralateral or ipsilateral?

Back 81

contralateral

(right ear stimulation is more represented in the left side of the brain)

Front 82

Where do the ascending nerves cross over in their ascension?

Back 82

dorsal/ventral cochlear nuclei

nuclei of lateral lemniscus

inferior colliculi

Front 83

98% of the neural auditory tract is

Back 83

afferent

Front 84

Most afferent nerve tracts are associated with the

Back 84

inner hair cells (95%)

(5% travel from outer hair cells)

Front 85

Most efferent nerve tracts are associated with the

Back 85

outer hair cells (80%)

(20% travel to inner hair cells)

Front 86

The efferent neuron of an inner hair cell has its synapse where?

Back 86

at the afferent neuron just below the hair cell

Front 87

The outer hair cell has what at its base?

Back 87

both afferent and efferent neuronal synapses

Front 88

What are the three innervation components of the cochlea?

Back 88

afferent bipolar cochlear sensor neurons

efferent neurons

autonomic nerve supply

Front 89

What are characteristics of afferent bipolar cochlear sensory neurons?

Back 89

also known as Type I cells

exclusively supply inner hair cells

make up 95% of spiral ganglion neurons

Front 90

Efferent neurons are also called

Back 90

centrifugal

Front 91

What are characteristics of Type II cells?

Back 91

unmyelinated monopolar neurons

afferent

supply outer hair cells

make up 5% of spiral ganglion neurons

Front 92

What are Type A cells?

Back 92

hair cells that receive both afferent and efferent nerve fibers

Front 93

What are Type B cells?

Back 93

hair cells that receive afferent fibers only

Front 94

Efferent innervation is organized according to

Back 94

the cells of origin in the brain stem

Front 95

How many nerve fibers supply the cochlea?

Back 95

30,000 afferent

1,800 efferent

Front 96

The efferent (centrifugal) nerve fibers constitute the

Back 96

olivocochlear bundle

Front 97

The principal effect of efferent nerve stimulation is

Back 97

inhibitory

Front 98

The cochlear branch of the auditory nerve is comprised of

Back 98

the central processes of the spiral ganglion cells

Front 99

How long is the auditory nerve?

Back 99

5 mm

Front 100

Third order neurons form a tract called the

Back 100

lateral lemniscus

Front 101

What is the end organ of hearing?

Back 101

the organ of Corti

Front 102

What are the primary sensory cells of the cochlea?

Back 102

inner and outer hair cells

Front 103

Cilia from which hair cells contact the tectorial membrane?

Back 103

outer hair cells

no cilia from inner hair cells contact the tectorial membrane

Front 104

Cilia act as

Back 104

micro-levers transmitting vibrations to the sensory-receptor cells

Front 105

What function do cilia perform?

Back 105

feed mechanical energy from the outer hair cells to the tectorial membrane

Front 106

What modifies the local electrical current that flows into the sensory-receptor cells?

Back 106

the cilia

Front 107

What are two ways the cilia on the outer hair cells are sheared?

Back 107

action of the traveling wave

the stiffness differential between the tectorial and basilar membranes

Front 108

Which hair cells will have more movement due to a traveling wave?

inner or outer?

Back 108

outer hair cells since the inner hair cells are located closer to the spiral lamina and will see less movement

Front 109

The lateral walls of outer hair cells are more like what?

Back 109

motile cells rather than sensory cells

Front 110

What is cytoplasm?

Back 110

substance of a cell exclusive of the nucleus

Front 111

What is reticulum?

Back 111

a fine network formed by cells

Front 112

What are cisternae?

Back 112

ultra microscopic spaces occurring between the membranes of the flattened sacs of cytoplasmatic reticulum

Front 113

What is actin?

Back 113

a protein in the mitochondria of the outer hair cells that aids in movement

Front 114

What do outer hair cells have that inner hair cells do not?

Back 114

specialized endoplasmic reticulum

lateral subsurface cisternae

Front 115

Outer hair cells can display what kind of movement?

Back 115

shortening and lengthening

Front 116

The first order neurons of the 8th nerve synapse where?

Back 116

at the dorsal and ventral cochlear nuclei

Front 117

The cochlear nuclei are located at the level of the

Back 117

medulla near the spinal cord

Front 118

What is another name for the dorsal cochlear nucleus?

Back 118

the acoustic tubercle

Front 119

Second order neurons ascend via what two routes from the dorsal cochlear nucleus?

Back 119

to the superior olivary complex
or
the nucleus of the lateral lemniscus

Front 120

What area is the nucleus of the lateral lemniscus located?

Back 120

at the level of the pons

Front 121

What forms the core of the brainstem?

Back 121

the reticular formation

Front 122

In the afferent auditory pathway, where do some fibers cross to the contralateral side?

Back 122

nucleus of the lateral lemniscus
and
the inferior colliculus

Front 123

In the afferent auditory pathway, fibers from the 3rd order travel from the geniculate body to where?

Back 123

via the auditory radiations through the internal capsule to

areas 41 and 42 in the superior temporal gyrus

Front 124

What are the structures of the afferent auditory pathway? (9)

Back 124

organ of Corti
spiral ganglion (1st order neurons)
dorsal/ventral cochlear nuclei (2nd order neurons)
superior olivary complex (2nd & 3rd order neurons)
trapezoid body
nucleus of lateral lemniscus (2nd, 3rd, & 4th order neurons)
inferior colliculus
medial geniculate body (3rd order neurons)
auditory cortex (superior temporal gyrus)

Front 125

What are the corresponding areas to the afferent auditory pathway?

Back 125

Medulla (cochlear nuclei)
Pons (lateral lemniscus)
Midbrain (inferior colliculus)
Thalamus (medial geniculate body)

Front 126

In the contralateral afferent pathway, how do the nerves cross over from the cochlear nuclei?

Back 126

three paths cross via the trapezoid body to the contralateral superior olivary complex

They are the dorsal stria, ventral stria and medial stria.

Front 127

In what area is the trapezoid body located?

Back 127

the cerebellopontine angle

(where the cerebellum and pons meet)

Front 128

In the contralateral afferent pathway, which of the three stria is the largest?

Back 128

the ventral stria

Front 129

The contralateral afferent pathway carries what fraction of the nerve fibers that reach the cortex?

Back 129

2/3

Front 130

The contralateral nerve fibers are more responsible for what compared to the ipsilateral pathway?

Back 130

speech intelligibility

Front 131

What is the efferent nerve pathway?

Back 131

cerebral cortex
inferior colliculus
lateral lemniscus
superior olivary complex
vestibular branch of 8th nerve
basal turn of the organ of Corti

Front 132

What are the various names of the efferent bundle?

Back 132

bundle of Oort
Rasmussen's bundle
olivo-cochlear bundle

Front 133

The efferent pathway has what effect on the cochlea?

Back 133

inhibitory and regulatory

Front 134

Inside the CANS, what fraction of efferent fibers are ipsilateral and how much are contralateral?

Back 134

1/5 ipsilateral

4/5 contralateral

Front 135

Where do the efferent fibers synapse?

Back 135

primarily at the outer hair cells
and
the non-myelinated dendritic portions of the afferent fibers at the inner hair cells

Front 136

How many nerve fibers from the organ of Corti comprise the auditory nerve?

Back 136

30,000

Front 137

The startle reflex is generated from what part of the afferent auditory pathway?

Back 137

the inferior colliculus

Front 138

The last afferent terminal in the brainstem is the

Back 138

medial geniculate body

Front 139

From the cochlear nucleus, neural impulses transfer to

Back 139

the ascending auditory pathway

Front 140

The auditory nerve travels how far between the cochlea and the brain?

Back 140

one inch

Front 141

What structures allow for neural impulses to switch between sides of the brainstem?

Back 141

cochlear nucleus
superior olive
inferior colliculus

Front 142

The contralateral pathway makes it easier to understand speech better with which ear?

Back 142

the right ear

(the contralateral pathway from the right ear goes to the left temporal lobe where the speech center is located)

Front 143

The auditory nerve is generally thought of as what kind of nerve?

Back 143

sensory

Front 144

How many nerve fibers carry efferent information?

Back 144

about 500

Front 145

What was Helmholtz's theory of hearing?

Back 145

Resonance theory

the mechanical resonant qualities of the cochlea allow it to perform spectral analysis of incoming sound

Front 146

What are the three beliefs Bekesy had about cochlea function?

Back 146

linear (input=output)
passive
broadly tuned

Front 147

Thomas Gold was an

Back 147

English physicist

Front 148

Gold believed the cochlea must possess

Back 148

a sharply tuned (narrow band) mechanical response system

Front 149

Gold concluded that, if the cochlea is narrowly tuned, then there must be

Back 149

a positive inner ear feedback element
(non-passive)

Front 150

What does EOAEs stand for?

Back 150

evoked otoacoustic emissions

Front 151

Who is David Kemp?

Back 151

an English physicist who, in 1978, demonstraed EOAEs

(motor theory of hearing)

Front 152

A damaged ear has what kind gain curve?

Back 152

flattened and rounded

Front 153

What is the result when outer hair cells are damaged?

Back 153

moderate hearing loss

frequency selectivity is reduced

otoacoustic emissions are absent

Front 154

What is the basis for the Motor Theory of Hearing?

Back 154

outer hair cells can act as both motor and sensory cells