Auditory System I & II

Question 1

waveform

Answer 1

amplitude of pressure vs. time

Question 2

Intensity

Answer 2

amplitude, measured in decibels where dB = 20log (p/p0) (where p=amplitude)

Question 3

p(0)

Answer 3

0.0002 dynes/cm^2

Question 4

frequency

Answer 4

cycles per second (Hz)

Question 5

physiology vs. physics

Answer 5

loudness:pitch::intensity:frequency – a big increase in pressure does not result in a comparable increase in loudness

Question 6

equal loudness curves

Answer 6

on a plot of intensity vs. frequency, dip where humans have the most acute hearing (1000-3000Hz)

Question 7

pitch and frequency

Answer 7

correlated but not related, 2pitch=3frequency

Question 8

pitch and amplitude

Answer 8

pitch is partially based on amplitude

Question 9

pitch in general

Answer 9

is more dependent on frequency than amplitude

Question 10

sound localization

Answer 10

uses temporal (phase) and intensity (amplitude) cues

Question 11

external outer ear composition and function

Answer 11

pinna (shadow at high frequencies - low frequencies slide through) and concha: together work as a resonator

Question 12

tympani membrane

Answer 12

boundary between outer and the middle ear

Question 13

middle ear

Answer 13

malleus, incus, and stapes (oval window). transfer of energy from a low to high impedance medium. HUGE amplification (mainly due to the size of the tympanic membrane vs. the oval window)

Question 14

2 muscles in the ear that decrease the effect of loud stimuli

Answer 14

tensor tympani (malleus, tension), stapedius (stapes, retraction)

Question 15

eustachian tube

Answer 15

connects the middle ear and the pharynx – pressure differences can cause pain/difficulty hearing

Question 16

cochlea

Answer 16

three chambers: scala vestibuli, scala tympani, scala media (organ of corti)

Question 17

organ of corti

Answer 17

is at the base of the scala media – includes structures from the tectorial to the basilar membrane. has inner and outer hair cells (efferent 75%)

Question 18

hair cells

Answer 18

have stereocillia at the apex connected by tip links. stimulated by the shearin gforces of the tectorial and basilar membranes. mechanical displacement yields action potentials

Question 19

endolymph vs. perilymph

Answer 19

+80mV, high K+ vs.

Question 20

potassium flow through the hair cell

Answer 20

apex (mechanosensitive, in, depolarization), base (Ca2+ activated, out, hyper-polarization) coupled with the opening of voltage gated Ca2+ channels. this de/hyperpolarization allows for a full sine curve at low frequencies

Question 21

phase locking

Answer 21

1:1 relationship between the sound wave and neuronal firing (1000 impulses/second)

Question 22

volley theory

Answer 22

a way of encoding pitch at low frequency (phase locking)

Question 23

sound input process

Answer 23

tympanic membrane compression –> bone lever –> push at oval window –> travel to helicotrema then to round window –> basilar membrane supports the wave from the oval window –> rarefraction pulls the stapes so fluid moves back towards the oval window (overall the compression followed by rarefraction causes the basilar membrane vibration along the organ of corti)

Question 24

basilar membrane

Answer 24

thickest and widest at the apex, apex stimulated by lower frequencies, hard to get resolution at low frequencies (handled by volley theory anyways)

Question 25

characteristic frequency

Answer 25

the frequency at which a given nerve is most sensitive (seen via a tuning curve)

Question 26

cochlear implants

Answer 26

require hair cells, utilize the tonotopic map of frequencies

Question 27

tonotopic map of frequencies is…

Answer 27

maintained all the way to the primary auditory cortex

Question 28

low frequency

Answer 28

spatial localization via phase shift, frequency encoding via volley theory

Question 29

high frequency

Answer 29

spatial localization via shadowing (intensity), frequency encoding via the tonotopic map

Question 30

3 theories for the encoding of sound intensity

Answer 30

1. neuron recruitment 2. increased probability of neural firing 3. loss of spatial resolution from loud stimuli 4.

Question 31

Sensorineuronal deafness

Answer 31

problem in bone conduction pathway, CN VIII

Question 32

conduction deafness

Answer 32

problem in the middle ear conduction

Question 33

rinne’s test

Answer 33

tuning fork, mastoid process to ear (normal: ear heard after bone, conduction deafness: bone > ear, sensorimotor deafness: both forms are diminished

Question 34

weber’s test

Answer 34

vertex of skull, normal: heard equally, conduction deafness: heard in abnormal ear first (wow!), sensorimotor deafness: sound louder in normal ear

Question 35

efferent auditory pathway

Answer 35

through the outer hair cells (75%), not related to tinnitus, correlated with a otoacoustical emission, thought to sharpen acuity and increase frequency resolution

Question 36

auditory nerve to cortex pathway

Answer 36

1.cochlear nuclei 2. superior olive 3. lateral lemniscus 3. inferior colliculus 4. medial geniculate 6. auditory cortex (superior olive/lateral lemniscus are not innervated by all fibers), most fibers ascend bilaterally, therefore a post cochlear lesion tends to result in a bilateral deficit

Question 37

MSO

Answer 37

medial superior olive, time based sound localization at low frequencies

Question 38

LSO & MNTB

Answer 38

lateral superior olive & the medial nucleus of the trapezoid body – sound localization, shadowing, high frequencies, excited by ipsi input, inhibited by contra input

Question 39

lateral lemniscus

Answer 39

only receives contralateral input, “onset” and “duration” of sounds

Question 40

inferior colliculus

Answer 40

auditory space map creation for sound localization, higher sound processing (i.e. speech)

Question 41

medial geniculate complex

Answer 41

temporal comparison

Question 42

primary auditory cortex

Answer 42

has tonotopic map, columnar organization(EE, EI - two vs. one ear excitation)

Question 43

secondary auditory cortex

Answer 43

inferior temporal lobe, complex sound processing (speech recognition centers)

Question 44

non dominant hemisphere (R)

Answer 44

processes emotional tone and inflections (L dominant processes speech)

Question 45

wernicke’s area lesion

Answer 45

word salad, inability to comprehend own deficit