Week 2 Lecture 6: Hearing and Equilibrium

Question 1

What senses is the ear responsible for?

Answer 1

Hearing and equilibrium

Question 2

What does the external ear consist of?

Answer 2

The pinna, ear canal, and tympanic membrane (or eardrum)

Question 3

Where is the middle ear located and what is it connected to?

Answer 3

The middle ear is after the eardrum and connected to the pharynx via the Eustachian tube

Question 4

What sensors does the inner ear contain and what senses do they correspond to?

Answer 4

The cochlea (hearing) and the vestibular apparatus (equilibrium)

Question 5

What is sound?

Answer 5

Pressure waves, at the peaks of the waves pressure is high and at the troughs pressure is low

Question 6

What is frequency?

Answer 6

The number of wave peaks per second

Question 7

What is frequency perceived as?

Answer 7

Pitch, low frequencies are low-pitched sounds, high frequencies are high-pitched sounds

Question 8

What is the measurement of frequency?

Answer 8

Hertz (Hz), waves per second

Question 9

What is the frequency range humans can hear?

Answer 9

16 to 20,000 Hz, 10 octaves

Question 10

What frequency range is aquity highest?

Answer 10

1000-3000 Hz

Question 11

What is amplitude?

Answer 11

The pressure difference between peaks and troughs

Question 12

How does amplitude play a factor in our perception of sound?

Answer 12

It determines our perception loudness, the larger the amplitude, the louder the sound

Question 13

What does also loudness depend on?

Answer 13

Frequency, if a sound is beyond the range of human hearing it won’t be perceived no matter how loud it is

Question 14

What do sound waves do to the eardrum

Answer 14

Vibrates the eardrum

Question 15

What bones carry the vibrations from the eardrum through the middle ear to the oval window?

Answer 15

The ossicles, the eardrum vibrates the malleus which move the incus which moves the stapes which pushes against the oval window.

Question 16

What is the oval window?

Answer 16

A membrane between the middle ear and the inner ear (cochlea)

Question 17

What does the cochlea contain?

Answer 17

Receptor cells

Question 18

What are the vestibular and tympanic ducts?

Answer 18

The vestibular and tympanic ducts are lateral ducts of the cochlea.

Question 19

What do the vestibular and tympanic ducts contain?

Answer 19

Perilymph, a fluid similar to plasma

Question 20

Where do the vestibular and tympanic duct communicate?

Answer 20

At the helicotrema

Question 21

What is the cochlear duct?

Answer 21

The medial duct of the cochlea

Question 22

What does the cochlear duct contain?

Answer 22

Endolymph, a fluid similar to intracellular fluid AND the organ of Corti

Question 23

What happens when the oval window vibrate?

Answer 23

Creates waves in the perilymph which shakes the cochlear duct

Question 24

What happens after the cochlear duct vibrates?

Answer 24

The wave energy eventually exits back into the middle ear via the round window

Question 25

Where is the organ of Corti located?

Answer 25

It sits on the basilar membrane and under the tectorial membrane

Question 26

What does the organ of Corti contain?

Answer 26

Auditory receptor cells (mechanoreceptors) called hair cells

Question 27

Are hair cells neurons?

Answer 27

No, they are epithelial cells (20,00 per cochlea)

Question 28

What does each hair cell have?

Answer 28

Stereocilla, 50-100 stiff hairs that extend into tectorial membrane

Question 29

What happen to stereocilla when there are waves in the perilymph?

Answer 29

They bend when waves in the perilymph deform the basilar and tectorial membrane

Question 30

When does the hair cell excite its primary sensory neuron (depolarizes/releases transmitter)?

Answer 30

When its cilia bends toward the longest cilium

Question 31

When does the hair cell releases less transmitter (hyperpolarizes)?

Answer 31

When its cilia bend away from its longest cilium

Question 32

How does the basilar membrane respond to different frequencies at different points?

Answer 32

High frequencies displace the basilar membrane at its stiff, narrow end near the oval window while low frequencies displace the basilar membrane and its wide, flexible end near the helicotrema

Question 33

What does the pattern of membrane motion reveal to the brain?

Answer 33

Pitch

Question 34

What is the pathway of auditory information?

Answer 34

Auditory nerve, cochlear nuclei in the medulla (crossing over), midbrain, medial geniculate nucleus of the thalamus and the auditory cortex

Question 35

Where is the primary auditory cortex (A1) located?

Answer 35

Temporal lobe

Question 36

What does the brain localize sounds based on?

Answer 36

Loudness and timing, if a sound is louder in the right ear it coming from the right side or if a sound reached the right ear before the left ear it is coming from the right side

Question 37

What are the different types of hearing loss?

Answer 37

Conductive, sensorineural and central

Question 38

What is conductive hearing loss?

Answer 38

Sounds cannot be conducted through external or middle ear

Question 39

What is sensorineural hearing loss?

Answer 39

Damage to the hair cells or elsewhere in the inner ear, most common in elderly (presbycusis) since hair cells cannot be replaced and are lost with age

Question 40

What is central hearing loss?

Answer 40

Damage to cortex or to the pathway between cochlea and cortex, patients usually have trouble interpreting/recognizing sounds

Question 41

What is the Rinne test?

Answer 41

Tuning fork is held against the mastoid bone and then beside the ear. If the sound is louder through the bone rather than beside the ear, there is conductive loss

Question 42

What is the Weber Test?

Answer 42

A tunic fork is held to the middle of the patient’s forehead. If the sound is louder in the good ear there is sensorineural loss. If it is louder in the bad ear ear there is conductive loss (doesn’t have to pass through ear canal)

Question 43

What are the utricle and saccule?

Answer 43

Parts of the vestibular apparatus that contain hair cells that are activated when the head tilts relative to gravity

Question 44

What are semicircular canals?

Answer 44

Part of the vestibular apparatus, fluid-filled hoops that detect head rotation

Question 45

Where vestibular pathways project?

Answer 45

Mainly to the cerebellum, vestibular hair cells activate primary sensory neurons of the vestibular nerve (cranial nerve 8) which either pass directly to the cerebellum or synapse in the medulla and proceed to the cerebellum or the thalamus (cortex)