Piri Lecture 1

Question 1

what are the steps of the auditory system

Answer 1

-sound waves transport energy which travels through the outer ear via the auditory canal and through the tympanic membrane (middle ear)
-they trigger hair cells on the cochlea’s organ of corti (inner ear) releasing neurotransmitters onto spiral ganglion cells
-spiral ganglion cells send information to the cochlear nuclei, superior olive, inferior colliculus, then to the thalamus, then finally the primary auditory complex

Question 2

infrasound

Answer 2

less than 20Hz (frequency lower than what humans can perceive)

Question 3

ultrasound

Answer 3

more than 20kHz (frequency higher than what humans can perceive)

Question 4

auditory canal

Answer 4

-“closed tuber resonator” (enhances sounds bw 2kHz and 5kHz
–part of the outer ear
-outer window exerts 20x pressure onto the tympanic membrane causing the amplification of the sound waves

Question 5

parts of the middle ear

Answer 5

-tympanic membrane
-ossicles (malleus, incus, stapes)
-eustachian tube

Question 6

what does the eustachian tube do

Question 7

attentuation reflex

Answer 7

contraction of muscles which are supposed to adjust fluid and amplify sound waves in the oval window/cochlea, protects against harmfully loud sounds

Question 8

perilymph

Answer 8

fills scala vestibuli and scala typani

Question 9

endolymph

Answer 9

fills scala media

Question 10

endolymph is _________ positive than perilymph which is important for the creation of _____________

Answer 10

more, endocochlear potential

Question 11

high concentration of sodium, low concentration of potassium

Answer 11

perilymph, scala vestibuli, scala tympani

Question 12

high concentration of potassium, low concentration of sodium

Answer 12

endolymph, scala media, due to the stria vascularis potassium pump maintaining this concentration

Question 13

if you unwind the cochlea, it is wider at the ______ and narrower at the _________

Answer 13

base, apex

Question 14

helicotrema

Answer 14

hole in the apex of the cochlea which connects the scala vestibuli and scali tympani (perilymphs)

Question 15

the basilar membrane is wider at the ________ and narrower at the __________

Answer 15

apex, base

Question 16

t/f: the basilar membrane is most stiff at the base and least stiff at the apex

Answer 16

true

Question 17

where do lower sound frequency waves travel to in the basilar membrane

Answer 17

the apex

Question 18

where do higher sound frequency waves travel to in the basilar membrane

Answer 18

the base (not as far)

Question 19

what is the organ of corti

Answer 19

the sensory area of the cochlea

Question 20

what do inner hair cells primarily synapse with

Answer 20

sensory afferents

Question 21

what do outer hair cells primarily synapse with

Answer 21

sensory efferents

Question 22

how are hair cells depolarized

Answer 22

-when stereocillia lean towards the largest stereocillium, tip links joining each stereocillium potassium channels loosen and potassium mechanoreceptor ion channels open
-stereocillia are in the endolymph (scala media), so high external potassium causes an influx into hair cells (depolarization)
-depolarization then causes the opening of voltage gated calcium channels downstream resulting in NT release

Question 23

which kind of hair cells detect most sound information

Answer 23

inner hair cells

Question 24

phase locking

Answer 24

the regular/pattern following consistent firing of hair cells for a given sound frequency, lost at higher frequencies

Question 25

lesion in the cochlear nucleus

Answer 25

ipsilateral loss of hearing

Question 26

lesion in the superior olive

Answer 26

partial loss of hearing

Question 26

lateral superior olive

Answer 26

encodes sound location through intensity differences,
-opposite side LSO is inhibited

Question 27

conductive hearing loss

Answer 27

issue w conduction of hearing loss in the outer or middle ear,

Question 28

sensorineural hearing loss

Answer 28

issue in cochlea/inner ear or pathway from cochlea to the brain

Question 29

left belt hemisphere of cortex

Answer 29

plays important role in speech processing

Question 30

right belt hemisphere of cortex

Answer 30

plays important role in tonal stimuli and music

Question 31

intraural time difference

Answer 31

-mechanism used to understand the location of sounds with frequencies under 2kHz
-accomplished via MSO neuron which fires most strongly when there are coincident synapses from the left and right ear sound waves
-if the sound is closer to the left ear, coincidence will occur farther away from left than right (sound wave via left ear will have more time to travel to MSO)