Auditory System

Question 1

What cranial nerve is part of the auditory system?

Answer 1

CN VIII

Question 2

CN VIII is SA or SE? What is it’s function?

Answer 2

SA, hearing and equilibrium

Question 3

What happens with lesion of the vestibulocochlear nerve?

Answer 3

Ipsilateral deafness
Loss of equilibrium

Question 4

Structures of the external ear

Answer 4

Auricle (pinna)
External acoustic meatus (external ear canal)
TM

Question 5

Structures of the middle ear

Answer 5

Malleus
Incus
Stapes

Question 6

What is the vestibule?

Answer 6

Inner ear bony structure encased by the temporal bone that is responsible for balance

Question 7

The vestibular labyrinth of the internal ear contains the following structures

Answer 7

Vestibule and 3 semicircular canals

Question 8

What does the vestibule contain?

Answer 8

Membranous utricle and saccule with macula as receptor organ

Question 9

What do the semicircular canals contain?

Answer 9

Semicircular ducts with ampullae

Question 10

What do the ampullae of semicircular ducts contain?

Answer 10

Crista ampullaris as receptor organ

Question 11

What are the general functions of the vestibular system?

Answer 11

1. Regulate body and limb posture through cerebellum and vestibulospinal tract
2. Regulate eye movements to keep eyes fixed on object when head is in motion

Question 12

What is the VOR reflex?

Answer 12

Vestibuloocular reflex
Regulates eye movements to keep eyes fixed on an object when head is in motion

Question 13

What is the function of the utricle?

Answer 13

Monitor and activate linear acceleration of horizontal movements
Side to side, front to back

Question 14

What is the function of the saccule?

Answer 14

Monitor and activate response to linear acceleration of vertical movements
Up and down

Question 15

What is the function of the three semicircular ducts?

Answer 15

Monitor and activate angular acceleration of head in all planes

Question 16

What are the three fluid-filled cavities (membranous cochlea) in the internal ear?

Answer 16

Scala vestibuli
Scala tympani
Scala media (cochlear duct)

Question 17

Which membranous cochlea contains the organ of corti?

Answer 17

Scala media

Question 18

What is the organ of corti?

Answer 18

Receptor organ of the auditory system

Question 19

The cochlear duct is the structure where sound travels from base to apex of the cochlea. Where are the high frequencies located? Low frequencies?

Answer 19

High frequencies: base
Low frequencies: apex

Question 20

Frequency of sound determines frequency of traveling wave in basilar membrane. Each traveling wave will maximally activate the basilar membrane a specific distance from base dependent on ____

Answer 20

Frequency

Question 21

Hair cells are ___ cells that are housed in ____

Answer 21

Receptor
Organ of corti

Question 22

Hair cells produce _____ transduction

Answer 22

Mechanoelectrical (convert movement into electrical signals)

Question 23

What causes depolarization of hair cells?

Answer 23

Stereocilia deflected toward tallest stereocilium
Pulls and stretches tip links which causes the cells to be more active

Question 24

What causes hyperpolarization of hair cells?

Answer 24

Stereocilia deflected towards shortest stereocilium
Presses tip links and makes them shorter which causes the cells to be less active

Question 25

There is __ hair cell for ___ stereocilia

Answer 25

One hair cell for many stereocilia

Question 26

Tip links ___ stereocilia

Answer 26

Connect

Question 27

The displacement of stereocilia of hair cells towards tallest stereocilium leads to conversion of

Answer 27

Movement into electrical signals, causes depolarization of hair cells and bipolar neurons

Question 28

The displacement of stereocilia of hair cells towards shortest stereocilium leads to

Answer 28

Hyperpolarization of hair cell and bipolar neurons

Question 29

Overview of the auditory pathway

Answer 29

First order neurons: CN VIII, spiral ganglion Second order neurons: Cochlear nuclei, pontine structures Inferior colliculus MGN neurons of thalamus Sublenticular limb of internal capsule Auditory radiation Primary auditory cortex

Question 30

What part of the internal capsule is part of the auditory pathway?

Answer 30

Sublenticular limb: axons from MGN neurons of thalamus to primary auditory cortex

Question 31

The primary auditory cortex is the ____(think structure)

Answer 31

Transverse temporal gyri of Heschl

Question 32

Where does higher level processing of the auditory cortex occur?

Answer 32

Downstream of the primary auditory cortex

Question 33

Blood supply of auditory system: the following structures are supplied by 1. Primary auditory cortex 2. Inferior colliculus and MGN 3. Pontine structures 4. Internal ear and cochlear nuclei

Answer 33

1. MCA 2. PCA 3. Basilar artery 4. AICA of basilar artery

Question 34

What structure is responsible for sound localization?

Answer 34

Superior olivary nuclei

Question 35

The superior olivary nuclei are responsible for

Answer 35

Receiving bilateral auditory input Important for localizing sounds in space

Question 36

What is air conduction?

Answer 36

Sound waves are sent through the external ear via air, vibrate TM, oscillate middle ear bones, activate inner ear neurons

Question 37

What is bone conduction?

Answer 37

Sound vibrations conducted to internal ear through temporal bone Bypass external and middle ear

Question 38

What is nerve (sensorineural) deafness?

Answer 38

Total ipsilateral deafness Neural pathway disrupted at or before cochlear nuclei

Question 39

What causes nerve (sensorineural deafness)?

Answer 39

Damage to hair cells or organ of corti Damage to spiral ganglion or CN VIII or cochlear nuclei Inflammation/infection in cochlea

Question 40

Are AC and BC affected by nerve deafness?

Answer 40

No

Question 41

What is central deafness?

Answer 41

Virtually no loss of hearing Difficulty in interpreting or localizing sounds Neural pathway disrupted at after cochlear nuclei

Question 42

Are AC and BC affected by central deafness?

Answer 42

No

Question 43

What is conduction deafness?

Answer 43

Partial ipsilateral deafness with interruption of air conduction of sound waves Neural pathway intact

Question 44

Causes of conduction deafness?

Answer 44

Inflammation/infection of EAM Cerumen buildup TM trauma or inflammation Otitis media Middle ear bone damage Otosclerosis

Question 45

Are AC and BC affected by conduction deafness?

Answer 45

AC: diminished or eliminated BC: unaffected

Question 46

Why is there virtually no loss of hearing with damage to proximal to cochlear nuclei?

Answer 46

Bilateralism that occurs in several locations of the auditory pathway

Question 47

Where does bilateralism occur in the auditory pathway?

Answer 47

Commissure of inferior colliculus Commisssure of lateral lemniscus Trapezoid body