The Ear and Hearing

Question 1

What is sound?

Answer 1

An oscillation of pressure through a compressible medium such as gas or liquid.

Question 2

What determines the pitch of a sound?

Answer 2

Frequency (Hz).

Question 3

What determines the volume of a sound?

Answer 3

Intensity (amplitude of pressure change).

Question 4

What is the human range of hearing?

Answer 4

20 Hz to 20,000 Hz.

Question 5

What are the main parts of the outer ear?

Answer 5

Pinna (auricle), external auditory meatus, tympanum.

Question 6

What is the function of the pinna?

Answer 6

Funnels sound, helps in vertical sound localisation, and filters human speech frequencies.

Question 7

What is the external auditory meatus lined with?

Answer 7

Hair, sebaceous glands, ceruminous glands.

Question 8

How much does the ear canal amplify human speech?

Answer 8

By 10–15 dB.

Question 9

What is the tympanic membrane?

Answer 9

A collagenous membrane that vibrates in response to sound waves.

Question 10

What are the ossicles of the middle ear?

Answer 10

Malleus, incus, stapes.

Question 11

What is the function of ossicles?

Answer 11

Act as a lever system, amplifying sound pressure by 20x.

Question 12

Which two muscles dampen middle ear sound?

Answer 12

Tensor tympani (CNV3) and stapedius (CNVII).

Question 13

What is the acoustic/attenuation reflex?

Answer 13

Muscle contraction in response to loud sounds or vocalisation.

Question 14

What is the function of the Eustachian tube?

Answer 14

Equalises pressure between middle ear and nasopharynx.

Question 15

Which nerve runs through the facial canal and crosses the middle ear?

Answer 15

Chorda tympani (taste to anterior 2/3 of tongue).

Question 16

What nerve innervates the stapedius?

Answer 16

Facial nerve

Question 17

What nerve innervates the tensor tympani?

Answer 17

Mandibular branch of trigeminal nerve (CNV3).

Question 18

What are the two main functions of the inner ear?

Answer 18

Balance (vestibular system) and hearing (cochlea).

Question 19

What converts mechanical energy into neural signals?

Answer 19

Inner ear fluid movement → hair cell activation → CN VIII.

Question 20

What are the two types of labyrinths?

Answer 20

Bony labyrinth (perilymph-filled), membranous labyrinth (endolymph-filled).

Question 21

What are the three scalae of the cochlea?

Answer 21

Scala vestibuli, scala media (cochlear duct), scala tympani.

Question 22

What structure contains the Organ of Corti?

Answer 22

Cochlear duct (scala media).

Question 23

What is the function of the Organ of Corti?

Answer 23

Converts mechanical vibration into action potentials.

Question 24

Where is high-frequency sound detected in the cochlea?

Answer 24

Base of cochlea.

Question 25

Where is low-frequency sound detected in the cochlea?

Answer 25

Apex (helicotrema).

Question 26

What do outer hair cells do?

Answer 26

Amplify mechanical input to inner hair cells.

Question 27

What do inner hair cells do?

Answer 27

Send sensory input to the brain via cochlear nerve.

Question 28

What causes hearing loss from noise?

Answer 28

Irreversible damage to hair cells.

Question 29

What is the order of the auditory pathway?

Answer 29

Organ of Corti Cochlear nerve Cochlear nuclei (cross over) Superior olivary complex Lateral lemniscus Inferior colliculus Medial geniculate nucleus Auditory cortex

Question 30

Where is the auditory cortex located?

Answer 30

Superior temporal gyrus (Brodmann areas 41 & 42).

Question 31

How are time differences detected?

Answer 31

Medial superior olivary nucleus (MSO).

Question 32

How are intensity differences detected?

Answer 32

Lateral superior olivary nucleus (LSO).

Question 33

How is vertical sound localisation achieved?

Answer 33

Shape of the pinna and body structures like head and shoulders.

Question 34

How does bone conduction differ from air conduction?

Answer 34

Bone conduction bypasses outer and middle ear and transmits vibration directly to inner ear.

Question 35

Why does your own voice sound deeper to you?

Answer 35

Bone conducts lower frequencies better.

Question 36

What is conductive hearing loss?

Answer 36

Problem in conducting sound through outer/middle ear.

Question 37

What is sensorineural hearing loss?

Answer 37

Damage to cochlea, CN VIII, or auditory cortex.

Question 38

What does the Rinne test compare?

Answer 38

Air conduction (AC) vs bone conduction (BC).

Question 39

What is a normal Rinne test result?

Answer 39

AC > BC.

Question 40

What indicates conductive hearing loss in Rinne test?

Answer 40

BC > AC.

Question 41

What result is seen in sensorineural hearing loss?

Answer 41

AC > BC, but both are reduced.

Question 42

What is the Weber test used for?

Answer 42

Lateralisation of hearing to determine type of unilateral hearing loss.

Question 43

In sensorineural loss, where is the sound heard louder?

Answer 43

Normal ear.

Question 44

In conductive loss, where is the sound heard louder?

Answer 44

Affected ear.

Question 45

What is the function of the ossicles?

Answer 45

Amplify and transfer sound from eardrum to inner ear.

Question 46

What part of the cochlea detects high-pitched sounds?

Answer 46

The base.

Question 47

What part of the cochlea detects low-pitched sounds?

Answer 47

The apex.

Question 48

What structure detects head position and movement?

Answer 48

Vestibular system.

Question 49

What type of fluid fills the cochlear duct?

Answer 49

Endolymph.

Question 50

What membrane contains the sensory cells for hearing?

Answer 50

Basilar membrane with the Organ of Corti.

Question 51

What structure lies at the base of the cochlear spiral and contains vascular and neural tissue?

Answer 51

The modiolus.

Question 52

What are the fluid-filled compartments of the cochlea and what do they contain?

Answer 52

Scala vestibuli – perilymph Scala media – endolymph Scala tympani – perilymph

Question 53

What separates the scala vestibuli from the scala media?

Answer 53

Reissner’s (vestibular) membrane.

Question 54

What separates the scala tympani from the scala media?

Answer 54

Basilar membrane.

Question 55

What part of the ear contains the Organ of Corti?

Answer 55

Cochlear duct (scala media).

Question 56

What triggers depolarisation of inner hair cells?

Answer 56

Shearing force causes hair cell stereocilia to deflect and open mechanically gated ion channels, allowing K⁺ influx from endolymph.

Question 57

Why does endolymph allow depolarisation with K⁺?

Answer 57

It has high K⁺ concentration, which enters the negatively charged hair cells when stereocilia bend.

Question 58

What is tonotopy?

Answer 58

Spatial arrangement where sound frequency is represented along the basilar membrane and preserved in auditory pathways up to the cortex.

Question 59

What property of the basilar membrane allows tonotopy?

Answer 59

It varies in stiffness and width along its length.

Question 60

Why can't the attenuation reflex protect against gunshots or explosions?

Answer 60

Reflex latency is 50–100 ms, which is too slow for sudden loud sounds.

Question 61

What hearing loss might occur with a CNVIII lesion?

Answer 61

Sensorineural hearing loss.

Question 62

What is presbycusis?

Answer 62

Age-related hearing loss, typically sensorineural, affecting high frequencies first.

Question 63

What is Ménière’s disease?

Answer 63

A disorder of the inner ear with vertigo, hearing loss, and tinnitus, associated with endolymphatic hydrops (increased pressure).

Question 64

What is otosclerosis?

Answer 64

Abnormal bone growth in middle ear, commonly at stapes footplate, leading to conductive hearing loss.

Question 65

What is the result of the Rinne test in conductive hearing loss?

Answer 65

Bone conduction (BC) > air conduction (AC).

Question 66

What is the result of the Weber test in unilateral sensorineural hearing loss?

Answer 66

Sound lateralises to the normal ear.

Question 67

Why does the Weber test lateralise to the affected ear in conductive hearing loss?

Answer 67

There's less ambient noise masking bone conduction in that ear.

Question 68

What frequency tuning forks are typically used for Rinne and Weber tests?

Answer 68

Rinne – 512 Hz Weber – 256 Hz (lower frequency for bone conduction detection)

Question 69

What are the utricle and saccule responsible for sensing?

Answer 69

Linear acceleration and head position relative to gravity.

Question 70

What structures detect rotational (angular) acceleration?

Answer 70

Semicircular canals (anterior, posterior, lateral).

Question 71

How is dizziness from vestibular dysfunction described?

Answer 71

Often as vertigo – a spinning or moving sensation.

Question 72

What makes the mammalian middle ear unique?

Answer 72

Presence of three ossicles – malleus, incus, and stapes.

Question 73

What ossicle do reptiles and birds have?

Answer 73

Only the stapes (columella in birds).

Question 74

What is the evolutionary origin of the malleus and incus?

Answer 74

Derived from jaw bones in early vertebrates.

Question 75

Mnemonic for ossicles in order of sound transmission?

Answer 75

MIS – Malleus → Incus → Stapes.

Question 76

Mnemonic for cochlear fluid compartments?

Answer 76

"VMT" Vestibuli (top) Media (middle) Tympani (bottom)