lec 5

Question 1

which structures are in the bony labyrinth? (3)

Answer 1

• cochlea
• semicircular canals
• utricle and saccule

Question 2

where is perilymph found? what about endolymph?

Answer 2

• perilymph: in the scala vestibuli + tympani
• endolymph: in the scala media

Question 3

which ion is perilymph high in?

Answer 3

Na+

Question 4

describe the movement of fluid through the cochlea

Answer 4

1. oval window > scala vestibuli > scala tympani > round window
2. also vertical movement that moves the scala media, organ or corti, hair cells etc…

Question 5

what would happen to the fluid if there was no round window?

Answer 5

would smash into bony wall

Question 6

what does “tonotopic organization” mean for the basilar membrane?

Answer 6

• base tunes high frequencies
• apex tunes low frequencies

Question 7

where is the organ of corti?

Answer 7

on the basilar membrane

Question 8

what is above the organ of corti?

Answer 8

tectorial membrane

Question 9

what is the function of the stria vascularis? (2)

Answer 9

• produces endolymph
• supplies oxygen and nutrients to cochlea

Question 10

what produces perilymph?

Answer 10

plasma

Question 11

90-95% of inner hair cells are ____ neurons.

90-95% of outer hair cells are ____ neurons.

Answer 11

• inner = afferent
• outer = efferent

Question 12

how are OHCs “cochlear amplifiers”? (2)

Answer 12

• pull tectorial + basilar membranes closer together for low intensity sounds, enabling IHCs to contact tectorial membrane
• sharpen peak of basilar membrane

Question 13

what do IHCs do regarding neurotransmitter? (2)

Answer 13

• change movement of stereocilia to release neurotransmitter
• neurotransmitter communicates with auditory nerve (and brain)

Question 14

T or F: at rest, stereocilia are polarized

Answer 14

true

Question 15

why do the stereocilia alternately depolarize and hyperpolarize?

Answer 15

to establish electric current that stimulates auditory fibres

Question 16

what is the alternating electrical current of the stereocilia called? what does it enable?

Answer 16

• cochlear microphonic
• enables sound to be converted to electrical energy so that it can be used by the auditory nerve

Question 17

which hair cells get damaged first? why? which frequencies are affected?

Answer 17

• OHCs
• constant shearing by tectorial membrane
• high frequencies

Question 18

what is presbycusis?

Answer 18

fancy word for age-related hearing loss!

Question 19

T or F: most of the auditory information processed by each half of the brain comes from the ipsilateral side.

Answer 19

FALSE – contralateral

Question 20

what does the peripheral auditory system refer to?

Answer 20

outer, middle, inner ear

Question 21

what is the main function of the afferent auditory pathways?

Answer 21

to transmit neural signals to the brain

Question 22

what are the 8 stations of the afferent auditory pathways?

Answer 22

1. cochlea
2. auditory nerve
3. cochlear nucleus
4. superior olive
5. lateral lemniscus
6. inferior colliculus
7. medial geniculate body
8. brain

Question 23

after the nerve fibres leave the cochlea, they go to the ___lateral cochlear nuclei.

Answer 23

ipsi

Question 24

what kind of frequencies are in the dorsal vs ventral cochlear nuclei?

Answer 24

• dorsal: high freqs
• ventral: low freqs
• some low freqs also go to ventral part of dorsal nucleus

Question 25

where do fibres go from the dorsal and ventral cochlear nuclei?

Answer 25

• dorsal: cross midline to lateral lemniscus
• ventral: 2/3 go to contra superior olivary complex, 1/3 go to ipsilateral SOC and then lateral lemniscus

Question 26

where do most fibres from the lateral lemniscus go?

Answer 26

• contralateral inferior colliculus
• some bypass it

Question 27

where do fibers go after the inferior colliculus?

Answer 27

ipsi or contral medial geniculate

Question 28

where do fibres go from the medial geniculate?

Answer 28

auditory cortex

Question 29

function of cochlear nucleus?

Answer 29

begin to process frequency and intensity of sounds

Question 30

function of superior olive? (3)

Answer 30

• helps in sound localization
• innervates middle ear reflexes
• protects ear from high intensity sounds

Question 31

function of lateral lemniscus? (3)

Answer 31

• integrative relay station
• sensitive to time + amplitude changes
• reduces spectral splatter

Question 32

function of inferior colliculus? (2)

Answer 32

• assists with temporal patterns and auditory space
• multi-modal sensory perception (“true multitasker”)

Question 33

function of medial geniculate? (2)

Answer 33

• distribution center for sensory info
• gets + keeps attention to sound

Question 34

function of auditory cortex? (4) where is it in the brain?

Answer 34

• discrimination and temporal aspects
• associating sound + past experience
• input from other senses
• memory of sounds
• in temporal lobes (heschl’s gyrus)

Question 35

function of secondary auditory cortex?

Answer 35

• harmonic, melodic, rhythmic patterns

Question 36

function of wernicke’s vs broca’s area? where are they?

Answer 36

• wernicke: understanding (temporal)
• broca: producing (frontal)

Question 37

what is the language loop?

Answer 37

both hearing a word + seeing a sign involve auditory cortex and wernicke’s area

Question 38

functions of occipital and parietal lobes related to speech?

Answer 38

• occipital: visual interpretation
• parietal: recognition of speech

Question 39

functions of brainstem and cerebellum related to speech?

Answer 39

• brainstem: message flow between brain and body
• cerebellum: controls speech muscles