Quiz 3

Question 1

Gain provided by Middle Ear

Answer 1

60 dB

Question 2

Acoustic Stapedial Reflex

Answer 2

-Stapedial muscle contracts in response to intense, long duration sounds

-Middle ear reflex by tone above 85 dB SPL

-Bilateral reflex

-May improve hearing in presence of ongoing loud sounds and head noises (speaking/chewing)

-Controlled by CN VII

-Tightens ossicular chain

Question 3

Number of cochlea turns

Answer 3

2.5

Question 4

3 compartments of the cochlea

Answer 4

-Scala Vestibuli (upper)
-Scala media (middle with neural components)
-Scala tympani (lower)

-Fluid in scala vestibuli is displaced by the movement of the stapes against the oval window. It travels to the apex of the cochlea and then travels back to the round window via the scala tympani.

-This causes basilar membrane to move

Question 5

Tonotopic Organization

Answer 5

-Pitches the basilar membrane (and other structures) are arranged in order

-BM decomposes complex sounds into their component sine waves

Question 6

Traveling Wave Envelope

Answer 6

-Low frequency almost all of BM undergoes displacement
-High frequency- restricted region is displaced

Question 7

Hair Cells

Answer 7

First neural component of auditory system

Question 8

Hair Cell Types

Answer 8

Three rows of outer hair cells, a ridge, and then one row of inner hair cells

Question 9

Inner Hair Cell Role

Answer 9

transduce sound into a neural impulse to the brain

-send signals to spiral ganglion

Question 10

Prestin shape change

Answer 10

The voltage-sensitive shape change feeds mechanical energy back into the basilar membrane

Question 11

OHC role

Answer 11

causes both an increase in amplification and frequency selectivity

-OHC allow you to focus in on frequency regions you care about

Question 12

Population coding

Answer 12

-Each neuron responds to the same phase of a sound

-Each neuron does not respond to the same period of the sound

-Timing of action potentials can tell you what the frequency was

Question 13

Ratio of IHC to spiral ganglion

Answer 13

1-to-10 ratio

Question 14

Cochlear Nucleus

Answer 14

-This is the first place where info from two ears are combined

-First stop for auditory information in the brainstem

-First major transformations of the signal occur here (Onset and Offset neurons)

Question 15

Superior Olivary Nucleus

Answer 15

-This structure is critical for azimuth based localizaton

-Plays a large role in descending pathway (jumping off point to OHC)

-Initiates pathways for processing interaural time differences

Question 16

Lateral lemniscus

Answer 16

the tracts formed of axons that project up to the midbrain from the superior olivary nucleus

Question 17

Inferior Colliculus

Answer 17

-Lateral lemniscus projects here

-Receives somatosensory inputs

-End of pathway for encoding interaural time differences

Question 18

Medial Geniculate Body

Answer 18

-Thalamic relay for auditory information

-Last stop before auditory cortex

-Interactions between auditory and visual information here

Question 19

Heschel’s Gyrus

Answer 19

-Auditory Cortex largely resides in superior region of the temporal lobe

-Primary auditory cortex located in Heschel’s gyrus

-First cortical processing of sound happens here

Question 20

What and Where pathways

Answer 20

-What: Identifying what you heard

-Where: Identifying where it came from

Question 21

Descending Pathway

Answer 21

-Allows you to selectively attend to sounds

-OHC most directly influenced by superior olivary nucleus

-Skips largely over cochlear nucleus on the way down

Question 22

Lateral olivocochlear pathway

Answer 22

efferents inhibit inner hair cell function

Question 23

Medial olivocochlear pathway

Answer 23

efferents inhibit outer hair cell function

Question 24

Both olivoochlear pathways

Answer 24

Reduce responses to soft sounds