THE AUDITORY SYSTEM

Question 1

scala vestibuli

Answer 1

the upper bony passage of the cochlea.

Question 2

scala media

Answer 2

The cochlear duct (or scala media) is an endolymph filled cavity inside the cochlea, located in between the tympanic duct and the vestibular duct, separated by the basilar membrane and Reissner’s membrane (the vestibular membrane) respectively.

Question 3

scala tympani

Answer 3

The tympanic duct or scala tympani is one of the perilymph-filled cavities in the inner ear of the human. It is separated from the cochlear duct by the basilar membrane, and it extends from the round window to the helicotrema, where it continues as vestibular duct.

Question 4

basilar membrane (BM).

Answer 4

The basilar membrane within the cochlea of the inner ear is a stiff structural element that separates two liquid-filled tubes that run along the coil of the cochlea, the scala media and the scala tympani

Question 5

Characteristic frequency

Answer 5

Neuron gets its input from a hair cell at a certain frequency ????

Question 6

Organ of Corti

Answer 6

a structure in the cochlea of the inner ear that produces nerve impulses in response to sound vibrations.

Within each cross section of the organ of Corti (Fig 4) there is one inner hair cell (IHC) and three (or 4) outer hair cells (OHCs)

Question 7

Intensity of sound coding

Answer 7

rate in which auditory nerve fibers fire

Level of the hair cells

At Characteristic frequency, a hair cell channel can open a little or a lot leading to different neurotransmitter release

Question 8

Hair cells

Answer 8

sensory receptors of both the auditory system and the vestibular. Through mechanotransduction, hair cells detect movement in their environment–> action potentials

Question 9

The deflection of the ______ opens mechanically gated ion channels that allow any small, positively charged ions (primarily potassium and calcium) to enter the cell.

Answer 9

hair-cell stereocilia

Question 10

The IHCs are attached to the BM due to their placement in the organ of Corti. Because of this, _________ (elicited by sound) are ultimately translated by IHCs into electrical signals

Answer 10

movements of this membrane

Question 11

helicotrema

Answer 11

part of the cochlear labyrinth where the scala tympani and the scala vestibuli meet

Question 12

Timing Coding

Answer 12

Phase locking
Keeps track of wave for timing
Fires at particular phase

Question 13

compression of the __________ sets up a so-called “traveling wave” that will reach a maximum amplitude at a certain location along the length of the BM

Answer 13

oval window

Question 14

Phase Locking

Answer 14

When auditory nerve neurons fire action potentials, they tend to respond at times corresponding to a peak in the sound pressure waveform, i.e., when the basilar membrane moves up.

Question 15

tonotopic map

Answer 15

Tones close to each other in terms of frequency are represented in topologically neighbouring regions in the brain. Tonotopic maps are a particular case of topographic organization, similar to retinotopy in the visual system

Question 16

1500 Hz is special because

Answer 16

Hair cells cannot track this

NT is released but not in relation to waveform of sound

Question 17

Auditory Neuropathy

Answer 17

transmission problem of
hair cell–> auditory nerve

Near normal audiogram

OHC work properly

Absent auditory brainstem response

Question 18

endocochlear potential

Answer 18

a magnitude of +80 mV (endolymph positive with respect to perilymph).

Question 19

The electric potential of endolymph is ~80-90 mV more positive than perilymph due to a higher concentration of ________

Answer 19

K compared to Na

Question 20

tip- links

Answer 20

Tip links are extracellular filaments that connect stereocilia to each other (hair cells of the inner ear)

Mechanotransduction is thought to occur at the site of the tip links, which connect to spring-gated ion channels

Question 21

tectorial membrane

Answer 21

acellular gels in the cochlea of the inner ear (the other being the basilar membrane (BM))

Question 22

How does the motion of the BM translate into displacement of the hair bundles?

Answer 22

BM and TM are attached at different points on the cochlear wall and thus have different pivot points.

Since the hair cells are attached to both the basilar and tectorial membranes, the ciliary bundles are pushed from side to side as a consequence of the shearing force. Current estimates of hair cell sensitivity suggest that it can reliably signal a bundle displacement of only a few angstroms

Question 23

auditory nerve fibers

Answer 23

basal end the hair cell is contacted by afferent fibers

2 types

Question 24

auditory nerve fibers

Type I ANFs innervate the ____ and are myelinated and Type II innervate the OHCs and are not myelinated.

Answer 24

IHCs

Question 25

The mechanical amplification of the displacement of the BM by OHCs is called the

Answer 25

cochlear amplifier.

Question 26

The cochlear nuclear complex comprises two nuclei:

Answer 26

the ventral cochlear nucleus and the dorsal cochlear nucleus.

Question 27

auditory nerve fibers

Type I ANFs innervate the IHCs and are myelinated and Type II innervate the _____ and are not myelinated.

Answer 27

OHCs