Chapter 52

Question 1

What are the 3 tubes in the cochlea?

Answer 1

o Scala vestibuli
o Scala media
o Scala tympani

Question 2

Which tube contains the organ of corti?

Answer 2

scala media

Question 3

What is the membrane called that separates the scala vestibuli and media?

Answer 3

Reissner’s/vestibular membrane

Question 4

What is inside of the organ of corti?

Answer 4

hair cells

Question 5

The basilar membrane separates which 2 tubes?

Answer 5

scala media and scala tympani

Question 6

High frequencies are best heard at which portion of the basilar membrane?

Answer 6

close to the oval window

Question 7

Medium frequencies are best heard at which portion of the basilar membrane?

Answer 7

middle of the basilar membrane

Question 8

Low frequencies are best heard at which portion of the basilar membrane?

Answer 8

at the apex of the membrane

Question 9

The nerve fibers from the hair cells lead to which ganglion?

Answer 9

spiral ganglion

Question 10

the spiral ganglion has fibers that make up which nerve?

Answer 10

cochlear nerve

Question 11

What are the stereocilia on the hair cells?

Answer 11

project upward from hair cells and are embedded in the tectorial membrane, which is in the scala media. Bending of the hair cells in 1 direction depolarizes the hair cells, and bending in the opposite direction hyperpolarizes them. This excites the auditory nerve fibers synapsing with their bases

Question 12

The outer ends of the ahir cells are fixed in a flat plate, which is called what?

Answer 12

reticular lamina

Question 13

True or false: the basilar fibers, rods of Corti, and reticular lamina move as a rigid unit.

Answer 13

True

Question 14

What does upward movement of the basilar fiber do to the reticular lamina?

Answer 14

rocks the reticular lamina upward and inward toward the modiolus

Question 15

What does downward movement of the basilar fiber do to the reticular lamina?

Answer 15

, the reticular lamina rocks downward and outward

Question 16

The thin filaments that attach the tips of the stereocilia cause what when the cilia are bent toward the scala vestibuli?

Answer 16

it opens K channels –> depolarization of the hair cell

Question 17

What is the place principle?

Answer 17

the major method used to determine different sound frequencies (typically higher pitched) by determining the positions along the basilar membrane that are most stimulated.

Question 18

What is the volley/frequency principle?

Answer 18

low freq sounds can cause volleys of nerve impulses synchronized at the same frequencies, and these volleys are transmitted by the cochlear nerve to the cochlear nuclei of the brain.

Question 19

What is the range (Hz) of human hearing?

Answer 19

20-20,000 Hz

Question 20

In old age, what can a person typically hear?

Answer 20

50-8,000 Hz

Question 21

After nerve fibers from the spiral ganglion of Corti enter the dorsal and ventral cochlear nuclei, where do they synapse?

Answer 21

onto 2nd order neruons, and decussate to other side (some stay on same side) to SOC

Question 22

From the SOC, how do the auditory fibers get to the thalamus?

Answer 22

SOC –> lateral lemniscus –> inferior colliculis –> medial geniculate nucleus

Question 23

From the MGB, how do the neurons get to the auditory Cx?

Answer 23

auditory radiations

Question 24

Where is the auditory Cx?

Answer 24

lies of the supratemporal plane of the superior temporal gyrus and extends to the lateral side of the temporal lobe + much of the insular cortex + some of the lateral portion of the parietal operculum

Question 25

What are the 2 parts of the auditory Cx?

Answer 25

1o auditory cortex (A1), and the auditory association cortex

Question 26

How many tonotopic maps are there in A1?

Answer 26

6

Question 27

Where are the low and high freq sounds heard for the tonotopic maps of A1?

Answer 27

Low frequencies are heard anteriorly, where high are posteriorly

Question 28

What happen if we removed the auditory cortex from a cat or monkey? Would they be able to still hear?

Answer 28

They would still be able to hear. However, it would greatly reduce the animal’s ability to discriminate different sound pitches and especially patterns of sound. Patterns meaning a sequential series of sounds one after another.

Question 29

What would happen if you have a lesion at the auditory association areas but not the primary Cx?

Answer 29

you can still hear and differentiate simple sound patterns. However, you can’t interpret the meaning of sound.

Question 30

What are the 2 mechanisms for determining the direction of sound?

Answer 30

1. The time lag between the entry of the sound into 1 ear and its entry into the opposite ear
2. Difference between the intensities of the sounds in the 2 ears.

Question 31

Direction of sound via time lag is best for what frequencies?

Answer 31

below 300 Hz

Question 32

Is time lag better or worse than intensity for determining direction? Why?

Answer 32

discriminates direction much more exactly than intensity because it does not depend on extraneous factors.

Question 33

Direction of sound via intensities is best for what frequencies?

Answer 33

higher frequencies because the head is a greater sound barrier at these frequencies

Question 34

How can you differentiate sounds coming in front of vs behind or above vs below?

Answer 34

by pinnae of the 2 ears: the shape of the pinna changes the quality of the sound entering the ear, depending of the direction where the sound comes from.

Question 35

Neuronal analysis for direction of sound begins at which structure?

Answer 35

SOC

Question 36

The SOC is divided into what 2 parts?

Answer 36

Medial and lateral superior olivary nuclei

Question 37

What does the lateral SOC recognize to determine direction for sounds?

Answer 37

by comparing the difference in intensities of the sound reaching the 2 ears. They then send appropriate signals to the auditory Cx to estimate the direction.

Question 38

What does the medial SOC recognize to determine direction for sounds?

Answer 38

detects the time lag between the signals from the 2 ears.

Question 39

How does the medial SOC recognize time lag? Give me the mechanism.

Answer 39

. It has a large # of neurons that have 2 major dendrites, 1 projecting to the right and 1 to the left. The sounds from the right ear impinge on the right dendrite, and the sounds from the left ear come signal the left dendrite. The intensity of excitation of each neuron is highly sensitive to a time lag. Some neurons respond maximally to a short time lag, and some respond maximally to a long time. Therefore we make up a spatial time pattern in the medial superior olivary nucleus, which can then tell the auditory cortex where the sound direction is coming from

Question 40

What is otosclerosis?

Answer 40

fibrosis of the middle ear following repeated infection or hereditary factors. Sound waves cannot be transmitted easily through the ossicles from the tympanic membrane to the oval window.