Auditory

Front 1

What is the function of the superior olivary nucleus in regards to hearing?

Back 1

localization of sound

Front 2

What is the function of the inferior colliculus in regards to sound?

Back 2

localization of sound

Front 3

What is the main thalamic relay point?

Back 3

medial geniculate

Front 4

What is the auditory cortex called?

Back 4

Heschl's gyrus

Front 5

Sound is a ________ wave that involves ________ increases and decreases.

Back 5

sinusoidal
pressure

Front 6

What is compression?

Back 6

increase in pressure

Front 7

What is rarefaction?

Back 7

decrease in pressure

Front 8

Is air an elastic or inelastic medium?

Back 8

elastic

Front 9

The molecules of air cause a __________ force on the eardrum.

Back 9

mechanical

Front 10

What is the normal hearing frequency range for humans?

Back 10

20 Hz - 20 kHz

Front 11

T/F: Humans can hear over a wide range of amplitudes.

Back 11

True

Front 12

Sound is measured in ______

Back 12

decibels (dB)

Front 13

L =

Back 13

20*log10 (Pmeasured/Preference)

Front 14

T/F: Humans are equally sensitive across frequencies.

Back 14

False

Front 15

Around what frequency do humans have the most sensitivity in hearing?

Back 15

1 kHz

Front 16

Damage occurs at or above ____ dB with persistent noise.

Back 16

120

Front 17

What is the central auditory pathway?

Back 17

cochlea --> cochlear nerve --> cochlear nucleus -->
a) some fibers cross in traapezoidal body and go through superior olives --> inferior colliculus
b)some fibers don't go throug trapezoid body but go straight to inferior colliculus
IC --> medial geniculate --> cortex

Front 18

Is hearing a unilateral or bilateral system? why?

Back 18

bilateral; as soon as fibers leave cochlear nucleus some of them cross to the other side

Front 19

What are the 3 fxns of the ear?

Back 19

1. sound collection
2. transmission and amplification
3. mechanical to electrical conduction

Front 20

What is the function of the outer ear?

Back 20

collection of sound and focusing sound on the eardrum

Front 21

What is the function of the middle ear?

Back 21

transmission of sound from eardrum to oval window

Front 22

What is the middle ear important for?

Back 22

amplification

Front 23

What fills the middle ear?

Back 23

air

Front 24

What is the function of the cochlea?

Back 24

convert mechanical energy to electrical signal

Front 25

What fills the chambers of the middle ear?

Back 25

perilymph

Front 26

What fills the scala media?

Back 26

endolymph

Front 27

What happens as sound travels through the middle/inner ear?

Back 27

vibrations cause oscillation of small bones --> pressure waves sent down perilymp filled chambers --> pressure released through membrane of round window

Front 28

What is the main transduction organ?

Back 28

organ of corti

Front 29

Where does the organ of corti sit? What semi encapsulates it?

Back 29

on the basilar membrane
tectorial membrane

Front 30

Where are the hair cells?

Back 30

in the region of the organ of corti

Front 31

What is the structure of the basilar membrane important for?

Back 31

frequency encoding (splits info info into component frequencies)

Front 32

Describe the basilar membrane structure.

Back 32

Near oval window it is narrower and less flexible
Near apex of cochlea it is wider and more flexible

Front 33

What kind of frequencies does the narrow, unflexible portion of the basilar membrane respond to/detect?

Back 33

high frequencies

Front 34

What kind of frequencies does the wide, flexible portion of the basilar membrane respond to/detect?

Back 34

low fequencies

Front 35

The frequency a cell transmits depends primarily on its __________.

Back 35

location on the basilar membrane

Front 36

What causes fluid within the ear to move?

Back 36

pressure differences

Front 37

What are traveling waves? What records these waves?

Back 37

pressure differences causes fluid to move;
basilar membrane records waves

Front 38

Are waves uniform across basilar membrane?

Back 38

no

Front 39

Basilar membrane oscillates differently for different _________.

Back 39

frequencies

Front 40

Where are basilar membrane oscilations at low frequency?

Back 40

low- near apex where membrane is widest

Front 41

Does a wave have the same amplitude as it moves across the entire membrane with time?

Back 41

no, waves quickly reduce in amplitude after their highest point so they aren't exciting other parts of the membrane

Front 42

From what is the endolymph derived?

Back 42

stria vascularis

Front 43

What is found in high concentration in the endolymph? Is this typical of extracellular media?

Back 43

potassium; no

Front 44

What is the function of outer hair cells?

Back 44

modulation of signal

Front 45

What is the function of inner hair cells?

Back 45

collecting auditory information

Front 46

There are a greater number of ____ hair cells.

Back 46

outer

Front 47

What is contained in the chamber below the basilar membrane? Does it have a high/low/normal K concentration?

Back 47

perilymph; normal K concentration

Front 48

What are the cilia of a hair cell in contact with?

Back 48

tectorial membrane

Front 49

How does K inter a hair cell? Why does K enter cell?

Back 49

through stereocilia; there is a huge driving force for K to enter cell

Front 50

What kind of membrane signal can be generated when K enters hair cell?

Back 50

a 20-30 mV signal

Front 51

What is the potential of the endolymph compared to the perilymph?

Back 51

endo is 80mV more positive than perilymph

Front 52

What is the membrane potential across the basilar membrane?

Back 52

-45 mV (normal for an excitable cell) (-45mV inside cell and 0 mV outside cell)

Front 53

What happens in the hair cell after the initial signal?

Back 53

depolarization and activation of voltage gated Calcium channels --> depolarization and vesicle release

Front 54

What kind of channels does initial depolarization activate?

Back 54

Ca and K

Front 55

What happens when K channels are activated?

Back 55

allows for extrusion of K into perilymph and dissipatation of signal

Front 56

Explain what happens in hair cell depolarization.

Back 56

basicallyl K moves from one side of the cell to the other and creates a depolarization which activates Ca channels

Front 57

What is the largest cilia in a hair cell?

Back 57

kinocilium

Front 58

Molecular links connect (individual cilia/isolated structures).

Back 58

individual cilia

Front 59

K channels are ____________-

Back 59

mechanosensitive

Front 60

What causes K channels to open?

Back 60

basilar membrane moves --> shearing between tips of cilia and tectorial membrane --> tension on tip link

Front 61

What determines whether K channels will open or close?

Back 61

the way the tectorial membrane bends

Front 62

What happens if the K channels close?

Back 62

hyperpolarization

Front 63

What is the proposed mechanism for hearing involving hair cells?

Back 63

-strong attachment between cilia and tectorial membrane
-as pressure changes in perilymph the membrane moves and there is shearing between tect. membrane and cilia

Front 64

The auditory canal is a ____________ channel.

Back 64

mechanosensitive

Front 65

What is the encoding frequency largely dependent upon?

Back 65

the properties of the basilar membrane itself

Front 66

What is the primary cause for deafness?

Back 66

loss or damage to hair cells

Front 67

What does a cochlear implant do?

Back 67

allows a person to bypass the hair cells by directly stimulating afferent nerve fibers

Front 68

What exactly is stimulated by a cochlear implant?

Back 68

the current produced by the stimulating electrodes must be sufficient to cause action potentials in the afferent fibers directly

Front 69

Why can't a cochlear implant stimulate the basilar membrane?

Back 69

even if it was able to vibrate the membrane - the hair cells are dead and so there would be no signaling

Front 70

Where is a cochlear implant placed?

Back 70

winded into the cochlea

Front 71

How does a cochlear implant work?

Back 71

-a microphone collects sound
-a processing unit splits it into various frequencies and sends them to wires which cause stimulation of the appropriate part of the basilar membrane

Front 72

T/F: With a cochlear implant you need to hit all frequencies in order to hear sound properly.

Back 72

F: You only need to hit certain frequencies

Front 73

What substance is hair cell synapse dependent upon?

Back 73

Ca++

Front 74

At a hair cell synapse, vesicles are arranged around a _______, _______ dense body and ultimately fuse and release __________ onto post-synaptic side.

Back 74

circular, electron dense;
glutamate

Front 75

T/F: Vesicle to post-synaptic plasma membrane fusion is the only fusion at a hair cell synapse.

Back 75

F: there may be fusion of vesicles to each other

Front 76

What are the four sets of nerve fibers in the auditory system and what do they innervate?

Back 76

1.2 olivocochlear efferents: brain --> inner and outer hair cells
2.primary afferents: inner hair cells
3.secondary afferents: outer hair cells

Front 77

Which type of hair cells are more sensitive and specific?

Back 77

inner hair cells

Front 78

What is the difference between inner and outer hair cells conveyance of sound to CNS?

Back 78

Inner: convergence of afferent fibers, each hair cell has 10 afferent outputs to CNS [1:10 ratio]
Outer: lots of divergence of afferent fibers [10:1 ratio]

Front 79

How many inner hair cells are there? outer hair cells?

Back 79

Inner: 3,500
Outer: 14,000

Front 80

What can depolarize outer hair cells?

Back 80

K+ or a patch electrode

Front 81

What happens when outer hair cells depolarized?

Back 81

the cells change shape by contracting or expanding

Front 82

How does cochlear fluid affect the sensitivity of outer hair cells?

Back 82

it dampens movement of the basilar membrane

Front 83

Outer hair cells have ______ efferent innervation and ______ afferent innervation

Back 83

extensive; limited

Front 84

What encodes loudness/intensity of sound?

Back 84

firing frequency of action potentials in nerve

Front 85

As sound increases the number of action potentials...

Back 85

increases.

Front 86

What is the saturation point for intensity?

Back 86

around 500Hz

Front 87

T/F: Perception of sound might not change much over higher range.

Back 87

True

Front 88

What 2 things does encoding frequency depend on?

Back 88

1. location of the cell on the basilar membrane
2. phase locking

Front 89

What is phase locking?

Back 89

If a sinusoidal wave brings information into the membrane and excites hair cells, the output gets locked to the phase of the waves.

Front 90

At a ____ frequency, information is lost but the position on the _________ is still present.

Back 90

high;
basilar membrane

Front 91

What modulates signals from inner hair cells? How?

Back 91

outer hair cells; when stimulated directly by efferents, they make inner hair cells less sensitive

Front 92

What can get rid of background noise? How?

Back 92

outer hair cells; background noise masks a tone but when the sensitivity is decreased (by outer hair cells) background noise is not detected as well

Front 93

In what 2 ways are outer hair cells important?

Back 93

1. increasing movement of basilar membrane (amplification)
2. changing the sensitivity of the inner hair cells and their afferent connections to the CNS

Front 94

Describe the ascending pathway of the auditory axis.

Back 94

CN VIII (spiral ganglion)
Cochlear nucleus
Superior Olivary nucleus
Lateral lemniscus
Inferior Colliculus
Medial geniculate body
Auditory cortex (transverse gyrus of temporal lobe)

Front 95

Describe the output of the cochlear nucleus.

Back 95

Some fibers cross in the trapezoid body and go to the superior olivary nucleus
Other fibers don't cross and go to the lateral lemniscus

Front 96

How do we know which direction the sound comes from?

Back 96

interaural timing differences and intensity differences

Front 97

Explain interaural timing differences

Back 97

When a sound comes in it is usually lateralized and hits one ear before the other which results in a timing difference between the two signals. The inner hair cells will be excited but one side will be delayed with respect to the other.

Front 98

With respect to sound localization, what variables change and which stay the same?

Back 98

change: frequency and wavelength
stay the same: distance between ears and speed of sound

Front 99

The time difference in sound is largely dependent upon ___________.

Back 99

angle to midline

Front 100

Cells in the medial superior olive respond best with __________ input. They are innervated __________ and ___________.

Back 100

Bilateral;
ipsilaterally and contralaterally (with slight delay in contralat.)

Front 101

Explain the mechanism of intensity differences in determinig sound localization.

Back 101

cells in the lateral superior olive respond better when a signal is less intense from one ear than from the other ear, a cell can respond strongly when stimulated by the ipsilateral side but not from the contralateral side

Front 102

What happens in the cells of the inferior colliculus?

Back 102

not much is known about processing here; a lot of the cells are sensitive to differences in aural delay and in intensity so thought to be involved in localization

Front 103

What is the main relay station in the thalamus to get information to the cortex?

Back 103

medial geniculate

Front 104

What are the cells in the medial geniculate sensitive to?

Back 104

-some are just sensitive to auditory information
-others are multimodal-sensitive to vision and somatosensation

Front 105

Where is the primary auditory cortex?

Back 105

temporal lobe (Heschl's gyrus)

Front 106

How are cells in the auditory cortex arranged?

Back 106

tontypically according to frequency

Front 107

In the auditory cortex within areas of high and low frequency, cells are sensitive to both ____ and _____ of sound.

Back 107

intensity and location

Front 108

The primary auditory cortex is near what other important structures?

Back 108

1.Broca's area of language processing and speech formation
2. Wernicke's area: speech comprehension