Physiology of the Auditory System

Question 1

Where is the basilar membrane displacement for high frequency noises?

Answer 1

at the base

Question 2

where is the basilar membrane displacement for lower frequency sounds?

Answer 2

more apical

Question 3

what is the structure of the membrane near the oval/round windows?

Answer 3

narrow and stiff

Question 4

what is the structure of the membrane near the helicotrema?

Answer 4

it is wider and more flexible

Question 5

how is the frequency of sound (pitch) coded?

Answer 5

by where along the basilar membrane there is greatest deflection

Question 6

what type of cells are hair cells?

Answer 6

they are mechanoreceptors

Question 7

what is on the apical end of hair cells?

Answer 7

stereocilia

Question 8

what is the ion composition of endolymph?

Answer 8

it is high in K+ but low in Na+

Question 9

where is endolymph found?

Answer 9

it fills the cochlear duct and the membranous labyrinth ; found in the scala media

Question 10

what is endolymph produced by?

Answer 10

stria vascularis

Question 11

what is the composition of perilymph?

Answer 11

it is potassium poor- low K+ but high Na+

Question 12

where is perilymph found?

Answer 12

it is found in the scala vestibuli and scala tympani

Question 13

what does the perilymph bathe?

Answer 13

the basal end of the cochlear hair cells

Question 14

what does the endolymph bath?

Answer 14

the apical end of the hair cells

Question 15

what happens when there is a pressure differential that will bend/ pivot the stereocilia in the direction of the longest stereocilia?

Answer 15

K+ ions will enter the cells and depolarize the cell

Question 16

what are the specific Ca2+ ion channels that open due to a change in voltage?

Answer 16

TRPA1

Question 17

deflection of stereocilia that causes depolarization will cause what?

Answer 17

release of the NT glutamate and a generation of action potentials in the 8th CN nerve fibers

Question 18

what happens when there is deflection of stereocilia towards the shortest stereocilia?

Answer 18

hyperpolarization

Question 19

what is the main role of the stria vascularis?

Answer 19

it maintains the electrochemical properties of the endolymph aka it keeps the scala media very highly concentrated with potassium

Question 20

what forms the blood-labyrinth barrier?

Answer 20

the high endocochlear potential drives positively charged ions into the hair cell down its concentration gradient

Question 21

what is a common source of ototoxic drug secretion into the cochlea?

Answer 21

the stria vascularis

Question 22

what is the primary function of the inner hair cells?

Answer 22

these are the primary source of auditory information

Question 23

what is the primary function of outer hair cells?

Answer 23

there are the primary cells that amplify sound waves; they are also contractile

Question 24

what are the olivocochlear efferents?

Answer 24

when the ear itself produces a sound- movement of the basilar membrane toward the oval window and through the middle ear

Question 25

what neurons innervate outer hair cells?

Answer 25

medial olivary complex neurons

Question 26

what neurons innervate inner hair cells?

Answer 26

lateral olivary complex neurons

Question 27

how can olivocochlear efferents be measured?

Answer 27

in the external auditory meatus as otoacoustic emissions (OAE)

Question 28

what is the clinical significant of OAE?

Answer 28

newborn hearing screening, ototoxicity, tinnitus

Question 29

what makes up the cochlear nuclear complex?

Answer 29

the ventral cochlear nuclei and the dorsal cochlear nuclei

Question 30

what is the role of the dorsal cochlear nuclei?

Answer 30

it integrates the acoustic information with somatosensory information

Question 31

what is the role of the ventral cochlear nuclei?

Answer 31

it begins processing the temporal and spectral features of the sound (nature of the sound- high/low)

Question 32

where is the first site in the brainstem where information from both ears converges?

Answer 32

the superior olivary complex

Question 33

what is the role of the superior olivary complex?

Answer 33

binaural processing

Question 34

what is binaural processing essential for?

Answer 34

to accurately localize sound

Question 35

what makes up the superior olivary complex?

Answer 35

the medial superior olivary nucleus and the lateral superior olivary nucleus

Question 36

what is the role of the medial superior olivary nucleus?

Answer 36

localizes sound due to differences in TIME of arrival to ears

Question 37

what is the role of the lateral superior olivary nucleus?

Answer 37

localizes sound due to differences in INTENSITY of sounds between ears

Question 38

what is the role of the inferior colliculus?

Answer 38

it suppresses information related to echoes and arrives at a final estimation of localization of sound along the horizon

Question 39

what is the relay station in the auditory pathway?

Answer 39

the medial geniculate nucleus of the thalamus

Question 40

what is essential in the conscious perception of sound?

Answer 40

the primary auditory cortex

Question 41

how is the set up of the primary auditory cortex?

Answer 41

more rostral areas are activated by low frequencies and more caudal areas respond to higher frequencies

Question 42

the auditory (secondary) association cortex is composed of multiple areas including what?

Answer 42

Broca's and Wernicke's

Question 43

what does the auditory association cortex respond to?

Answer 43

more complex sounds such as music, identifying (naming) a sound, and speech

Question 44

where do olivocochlear efferents originate?

Answer 44

in the superior olivary complex

Question 45

what is the primary role of the olivocochlear efferents?

Answer 45

they decrease basilar basilar membrane motion- reduces responses to noise- may protect hair cells from damage to intense sounds

Question 46

the middle ear efferents include motor innervation to what?

Answer 46

tensor tympani to the malleus and tympanic membrane and the stapedius to the stapes

Question 47

when do middle ear efferents act and what may they prevent?

Answer 47

they act at low frequencies and they may prevent damage

Question 48

what is sensorineural hearing loss caused from?

Answer 48

damage to the hair cells or nerve fibers or both

Question 49

injury to outer hair cells causes what?

Answer 49

decrease in sensitivity

Question 50

injury to inner hair cells causes what?

Answer 50

it cuts off auditory input to the CNS

Question 51

what is the anterior semicircular canal activated by?

Answer 51

rotation in the vertical plane forwards (falling forward)

Question 52

what is the horizontal semicircular canal activated by?

Answer 52

rotation in the horizontal plane (twirling like ice skating)

Question 53

what is the posterior semicircular canal activated by?

Answer 53

rotation in the vertical plane backwards (falling backwards)

Question 54

what is the utricle activated by?

Answer 54

linear acceleration forward and backward (running)

Question 55

what is the saccule activated by?

Answer 55

linear acceleration up and down (dunking a hoop)