Auditory Physiology

Question 1

What is sound?

Answer 1

Oscillations of air pressure

Question 2

What is amplitude?

Answer 2

Sound pressure (intensity) measured in Decibels

Question 3

What is frequency?

Answer 3

Number of oscillations of air pressure per second measured in Hz

Question 4

Describe the properties of the basilar membrane?

Answer 4

It is narrow and STIFF near the oval/round windows

It is wider and FLEXIBLE near the apex (helicotrema)

Question 5

Motion at the base of the basilar membrane is done by?

Answer 5

High pitched sounds (high frequencies)

Question 6

Motion at the apical end of the basilar membrane is done by?

Answer 6

Low frequency (pitched) sounds

Question 7

The frequency of sound is coded by?

Answer 7

Where along the basilar membrane there is the greatest DEFLECTION

Question 8

High pitched sounds deflect the basilar membrane where?

Answer 8

Near the round/oval windows at its base

Question 9

Low pitched sounds deflect the basilar membrane where?

Answer 9

Near the helicotrema near its apex

Question 10

What type of receptors are hair cells?

Answer 10

Mechanoreceptors

Question 11

Are hair cells neurons?

Answer 11

Nope

Question 12

What exists on the apical surface of hair cells?

Answer 12

Stereocilia

Question 13

What protein is within stereociliar?

Answer 13

Actin

Question 14

What can be found at the basal end of stereociliar?

Answer 14

Afferent and efferent nerve fiber synapses

Question 15

Levels of potassium and sodium in Endolymph?

Answer 15

HIGH K and low na

Question 16

Levels of potassium and sodium in Perilymph?

Answer 16

LOW K and high na

Question 17

Does endolymph or perilymph bath the apical surface of hair cells?

Answer 17

Endolymph = apical end
Perilymph = basal end

Question 18

As the basilar membrane is deflected by sound, it moves the hair cells against the tectorial membrane. What way must the stereocilia be deflected in order to depolarize?

Answer 18

TOWARDS the tallest stereocilia

Question 19

As the stereocilia at deflected towards the tallest one, what is opened?

Answer 19

Mechanically gated K+ channels and potassium enters cell

Question 20

____ connects stereocilia and the force is transmitted to ______

Answer 20

Tip links

Elastic gating spring

Question 21

Once potassium is allowed into hair cells, then what happens?

Answer 21

TRPA1 channels are opened and Ca++ enters the cell

Question 22

What ions come into the hair cell to depolarize it and allow for NT release?

Answer 22

K and Ca

Question 23

What neurotransmitter is released from hair cells?

Answer 23

Glutamate

Question 24

If the stereocilia at deflected towards the smallest stereocilia, what happens?

Answer 24

Hyperpolarization

Question 25

What produces endolymph?

Answer 25

Stria vascularis

Question 26

Where is the stria vascularis?

Answer 26

In the scala media

Question 27

As the stria vascularis produces endolymph (high in K+), what does this create for the scala media?

Answer 27

A resting membrane potential of +80 mv

Question 28

The potential of +80 mv in the scala media creates what?

Answer 28

Drives (+) ions down their conc. gradient into hair cells and creates a blood-Labyrinth Barrier (BLB)

Question 29

Any substance that crosses _____ can damage/impact hearing by hurting the stria vascularis?

Answer 29

BLB - blood labyrinth barrier

Question 30

Inner hair cells are?

Answer 30

Primary source of auditory info

Question 31

Inner hair cells are arranged into a ___ layer

Answer 31

single

Question 32

Outer hair cells act as?

Answer 32

An amplifier of sound

Question 33

Outer hair cells are arranged into ____ rows

Answer 33

3

Question 34

What property allows the outer hair cells to amplify sound?

Answer 34

They are contractile epithelial cells and when they contract, it further displaces the basilar membrane!

Question 35

When the ear itself produces sound it is known as?

Answer 35

Otoacoustic emissions (OAE)

Question 36

Describe how an ear can itself produce sound?

Answer 36

Impulses originate at the superior olivary complex - Olivocochlear efferents go to outer hair cells - Outer hair cells then contract and displace the basilar membrane which produces sound that travels back out middle hear and to tympanic membrane

Question 37

2 types of OAE

Answer 37

Spontaneous and Evoked

Question 38

Evoked OAE test?

Answer 38

Hearing loss on infants | - Evoked emissions will NOT be present if there is hearing loss

Question 39

Posterior cochlear nuclei

Answer 39

Integrates acoustic information with somatosensory

Question 40

Anterior cochlear nuclei

Answer 40

Begins processing temporal and spectral features of sound

Question 41

Medial superior olivary complex

Answer 41

Generates a map of interaural TIME differences to help localize location of sound

Question 42

Lateral superior olivary complex

Answer 42

Generates a map of interaural INTENSITY differences

Question 43

Inferior colliculus

Answer 43

Suppressed information related to echoes and creates a precise origin of sound location

Question 44

Medial geniculate nucleus

Answer 44

Relays all information about sound to the primary auditory cortex

Question 45

Primary auditory cortex

Answer 45

Conscious perception of sound

Question 46

What is the arrangement of the primary auditory cortex?

Answer 46

Rostral regions = low freq. sound | Caudal regions = high freq. sound

Question 47

What does the secondary auditory cortex respond to?

Answer 47

More complex sounds like music and identifying/naming a sound

Question 48

The secondary auditory cortex includes?

Answer 48

Broca's and Wernicke's areas

Question 49

What are the efferent innervations in the ear?

Answer 49

Olivocochlear, Middle ear muscle motoneurons, autonomic innervation of inner ear

Question 50

What do olivocochlear efferents do?

Answer 50

In response to LOUD noises, they decrease basilar membrane motion and protect hair cells

Question 51

What do middle ear muscle motoneurons do?

Answer 51

In response to LOUD noises, bilateral contraction to reduce transmission of sound and prevent damage

Question 52

What are the middle ear muscles?

Answer 52

Tensor tympani and stapedius

Question 53

What is the autonomic innervation of the inner ear comprised of?

Answer 53

Sympathetic adrenergic fibers

Question 54

What causes Sensorineural hearing loss?

Answer 54

Damage to hair cells or nerve fibers or both

Question 55

Which type of hair cell is more susceptible to injury?

Answer 55

Outer hair cells

Question 56

Damage to outer hair cells?

Answer 56

Decrease sensitivity to sound

Question 57

Damage to inner hair cells?

Answer 57

Cut off auditory input to CNS

Question 58

How to cochlear prostheses restore some hearing?

Answer 58

Electrode array threaded through cochlea and stimulates surviving nerve fibers

Question 59

Part of ear activated by forward motion

Answer 59

Anterior semi-circular canals

Question 60

Part of ear activated by backward motion

Answer 60

Posterior semi-circular canals

Question 61

Part of ear activated by rotation

Answer 61

Horizontal semi-circular canals

Question 62

Part of ear activated by linear acceleration forward and backward

Answer 62

Utricle

Question 63

Part of ear activated by linear acceleration up and down

Answer 63

Saccule

Question 64

What are the main structures that are involved in the pathway of sound processing?

Answer 64

``` Cochlear nuclei Superior olivary complex Inferior colliculus Medial Geniculate nucleus Primary auditory cortex ```

Question 65

What innervates outer hair cells?

Answer 65

Medial olivary complex neurons

Question 66

What innervates inner hair cells?

Answer 66

Lateral olivary complex neurons