AnaPhy of the Auditory System

Question 1

Encases the ear

Answer 1

Temporal Bone

Question 2

Most visible part of the ear
Composed primarily of cartilage

Answer 2

Pinna/Auricle

Question 3

What gives pinna its unique shape and size?

Answer 3

Concavities

Question 4

What are the functions of the pinna?

Answer 4

Sound collection (funneling sound in)

Sound localization (ability to locate where sound is coming from)

Question 5

Sounds arrive earlier in ear closest to sound source

Answer 5

Interaural timing difference

Question 6

Difference in sound level due to head shadow effect and distance

Answer 6

Interaural level differences

Question 7

Unique size and shape of pinna helps us determine where along vertical plane sound is coming from

Answer 7

Pinna effect

Question 8

S-shaped canal; Access route to tympanic membrane

Answer 8

External Auditory Canal / External auditory meatus

Question 9

What are the functions of the EAC?

Answer 9

For sound transmission
For sound resonation - amplification

Question 10

Underlies the self-cleaning mechanism of the ear canal and removal of wax

Answer 10

Epithelial migration

Question 11

Inflammation of outer ear

Answer 11

Otitis externa

Question 12

Pushed earwax further into the ear

Answer 12

Impacted cerumen

Question 13

Canal bends

EAC is short, straight and directed upwards

Answer 13

<3 years old

Question 14

In children >3 years old, EAC is

Answer 14

S-shaped, long, directed downwards

Question 15

To fully inspect the ears, we need to straighten the ear canals first then …

Answer 15

pull pinna down and back for <3 years old

pull pinna up and back for >3 years old

Question 16

Pinna missing completely

Answer 16

Anotia

Question 17

Pinna is small and not formed properly

Answer 17

Microtia

Question 18

EAC missing completely

Answer 18

Atresia

Question 19

EAC small/narrow

Answer 19

Stenosis

Question 20

Grade at which the upper ear is severely deficient + the ear canal may be present or absent

Answer 20

Grade 2

Question 21

Grade at which the ear is smaller but still looks like an ear

Answer 21

Grade 1

Question 22

Grade at which the ear canal is absent

Answer 22

Grade 3

Question 23

Grade at which there’s Anotia and Atresia

Answer 23

Grade 4

Question 24

Elastic, thin, and cone shaped structure that is flexible and tough

Answer 24

Tympanic Membrane

Question 25

Functions of the tympanic membrane

Answer 25

Protection Sound Transmission

Question 26

Only part of the tympanic membrane that is involved in transmission of acoustic energy from outer ear to middle ear; Larger, stiffer portion

Answer 26

Pars Tensa

Question 27

Lax part of the Tympanic Membrane

Answer 27

Pars Flaccida

Question 28

Middle ear inflammation Common in children between 6-11 months

Answer 28

Otitis Media

Question 29

Complication of Chronic Otitis Media Build up of fluid in the middle ear space → pressure → TM bursts Hearing loss of 0-40dB

Answer 29

Perforation

Question 30

Smallest bones in the body that conducts sound from middle to inner ear

Answer 30

Ossicles

Question 31

3 bones in the ossicular chain

Answer 31

malleus, incus, stapes

Question 32

Where is the malleus attached to the TM?

Answer 32

Manubrium

Question 33

Where is the stapes attached to the oval window?

Answer 33

via its foot plate

Question 34

Bilateral reflex that protects against loud sounds

Answer 34

Acoustic reflex

Question 35

Main muscle for Acoustic reflex

Answer 35

Stapedius

Question 36

other muscle involved in the Acoustic reflex

Answer 36

Tensor tympani

Question 37

Time delay of ____ is present for acoustic reflex and this presents a problem for sudden loud sounds

Answer 37

200 ms

Question 38

Connects middle ear to the nasopharynx

Answer 38

Eustachian Tube

Question 39

Function of the Eustachian Tube

Answer 39

Maintain air pressure within middle ear

Question 40

Opens the Eustachian Tube during swallowing and yawning

Answer 40

Tensor Veli Palatini (CN 5, Trigeminal)

Question 41

In infants and small children, eustachian tube is narrower, shorter and more horizontal TRUE OR FALSE?

Answer 41

TRUE

Question 42

Allows a sound wave travelling in air (in the outer ear and middle ear) to become a sound wave travelling in fluid (in the inner ear)

Answer 42

Middle Ear Transformation System

Question 43

METS: High surface of TM → push small surface of oval window (caused by the pushing of the stapes footplate) Gain Approx. : 25 dB

Answer 43

Areal ratio

Question 44

METS: TM parts do not move in unison with one another → generates additional force Gain Approx. : 6 dB

Answer 44

TM buckling effect

Question 45

METS: Stapes → oval window → (upper chamber) scala vestibuli → apex → (lower chamber) scala tympani → round window will move forward and back → generates additional energy pabalik sa taas Gain Approx. : 4 dB

Answer 45

Window phase differential

Question 46

Innervation of the Conductive Pathway

Answer 46

CN 5 (Trigeminal) CN 7 (Facial) CN 9 (Glossopharyngeal) CN 10 (Vagus)

Question 47

2 Labyrinths on the Inner Ear: ___ - contains perilymph → encases the: Membranous - contains ___

Answer 47

Bony, endolymph

Question 48

Resembles a snail shell; a coiled structure

Answer 48

Cochlea

Question 49

3 SCALA of the Cochlea

Answer 49

Scala vestibuli, scala media, and scala tympani

Question 50

2 MEMBRANES of the Cochlea

Answer 50

Reissner’s membrane and basilar membrane

Question 51

Contains several thousand hair cells/cilia that respond to vibrations of basilar membrane

Answer 51

Organ of Corti

Question 52

2 Major Structures of the Organ of Corti

Answer 52

Hair Cells (Inner & Outer) Basilar Membrane

Question 53

Main structure that supports the traveling wave, responsible for the frequency tuning/ tonotopicity of the cochlea

Answer 53

Basilar Membrane

Question 54

Base of the BM is narrow and stiff; responsible for

Answer 54

High Frequency

Question 55

Apex of the BM is wider and more flaccid; responsible for

Answer 55

Low Frequency

Question 56

Vibration of the basilar membrane gets picked up by hair cells

Answer 56

Transduction of Sound

Question 57

Transduction of Sound up to the Central Pathway. Explain.

Answer 57

Stapes → oval window → scala vestibuli → apex → scala tympani → move basilar membrane in scala media → vibration of the BM gets picked up by the hair cells → OHC comes in contact with the TM (jump and twitch) → motion of the TM is influenced (shearing motion)→ comes in contact with the IHC → stereocilia (hair-like structures on the IHC) bends → tip links (mechanically gated channels between the stereocilia where calcium and potassium enters) opens → triggers an electrical response (inflow of calcium and potassium inside the hair cell) → depolarization of the HC → release of neurotransmitter → can communicate with the auditory nerve → exits at the IAC → Fibers now terminate at the cochlear nucleus → synapse with neurons that ascend to the inferior colliculus which further extend to the medial geniculate body of the thalamus → neurons project to the auditory cortex (main area for auditory processing

Question 58

Cochlear amplifier; jump and “twitch” to increase vibration along basilar membrane

Answer 58

Outer Hair Cells

Question 59

True sensory neurons

Answer 59

Inner Hair Cells

Question 60

Coding for Frequency: _____ Via the basilar membrane Base (narrow and stiff): high freq. Apex (wider and more lax): low freq.

Answer 60

Traveling Wave

Question 61

Coding for Intensity: ______ Number of neurons firing (recruitment) ↑ recruitment = ↑ intensity

Answer 61

Rate of neural activity

Question 62

CN 8

Answer 62

VESTIBULOCOCHLEAR NERVE

Question 63

Hair cell receptors synapse with the ____ branch of CN 8

Answer 63

Cochlear branch

Question 64

Vestibular branch - Innervates the vestibular apparatus include the ___ of your inner ear

Answer 64

Semicircular canals

Question 65

VCN exits through the ____

Answer 65

Internal auditory canal