Hearing

Question 1

What are sound waves?

Answer 1

compression and decompression of the air (rarefaction) that reach your ears and allow to hear sounds

Question 2

What is amplitude? How is it measured?

Answer 2

depth of the lowering and of the raising of the wave, measured in decibels (dB)

Question 3

At which decibel levels are we feeling pain?

Answer 3

Above 130dB = pain

Question 4

What level of decibel can cause hearing loss if heard for a prolonged period of time?

Answer 4

Above 85dB for prolonged time = hearing loss

Question 5

What level of decibel causes immediate hearing loss?

Answer 5

Near sound above 120dB = immediate hearing loss

Question 6

What is sensorineural hearing loss?

Answer 6

type of deafness caused by high-decibel sounds

Question 7

What is frequency? How is it measured?

Answer 7

cycles per second that the wave has, measured in Hertz(Hz)

Question 8

What is the range of frequencies that humans perceive?

Answer 8

Humans perceive sounds between 20 and 20,000 Hz (outside of this we don’t hear the sounds)

Question 9

How is amplitude perceived?

Answer 9

Amplitude is perceived as the loudness of the sound

Question 10

How is frequency perceived?

Answer 10

Frequency is perceived as the pitch of the sound

Question 11

Are frequency and amplitude dependent?

Answer 11

No

Question 12

What is the pinna? What does it do?

Answer 12

visible part of the ear (Collects sound from the environment and localizes them)

Question 13

What is the auditory canal?

Answer 13

Conducts sounds energy from outer to middle ear

Question 14

What are the parts of the middle ear?

Answer 14

Eardrum (tympanic membrane) and ossicles (3 bones)

Question 15

What are the ossicles’ names?

Answer 15

• Malleus, incus, and stapes (amplify sounds coming from outside to transfer them to the cochlea)
• Stapes connects to inner ear at the oval window

Question 16

What are the parts of the inner ear?

Answer 16

• Cochlea (contains receptors responsible for transducing energy from sound waves to electrical impulses)
• Semicircular canals (play a role in balance)

Question 17

what are the 3 chambers of the cochlea?

Answer 17

• Scala timpani (Lower part)
• Scala media (middle part - organ of Corti)
• Scala vestibuli (upper part)

Question 18

What does the cochlea coils around?

Answer 18

Coils around a bony pillar called the modiolus

Question 19

What are the 2 types of fluids in the cochlea chambers?

Answer 19

• Endolymph (scala media)

* Perilymph (scala tympani and scala vestibuli)

Question 20

How is called the membrane separating the organ of Corti from the scala tympani?

Answer 20

Basilar membrane

Question 21

How is called the membrane separating the organ of Corti from the scala media?

Answer 21

Tectorial membrane

Question 22

What are hair cells? Where are they located?

Answer 22

• Includes tectorial membrane
• Hair cells connect to ganglion cells, which carry info to the brain
• Outer hair cells closer to tectorial membrane and inner hair cells closer to basilar membrane

Question 23

How is the basilar membrane differentially affected by the different wavelengths of sounds?

Answer 23

Because of its shape
• Thick at the base: high-frequency cannot move pat the beginning of the structure (peaks are observed early on)
• Low frequency waves are less affected by the thickness (tend to peak further down the apex)

Question 24

What are mechanoreceptors?

Answer 24

activated when subjected to deformation (they are modified epithelium and not neurons)

Question 25

What are stereocilia and what do they do?

Answer 25

• Stereocilia are embedded in the tectorial membrane and bend towards the kinocillium (positive direction) during the peak of a wave, depolarizing the membrane (increased afferent fiber firing)
• Bend away from kinocillium (negative direction) - cells hyperpolarize (no action potential) (decreased afferent fiber firing)

Question 26

Stereocilia and ____ form the hair bundle

Answer 26

Cilium (true cilium or kinocilium)

Question 27

Do hair cells have dendrites and axons?

Answer 27

No

Question 28

What are the roles of inner and outer hair cells?

Answer 28

• Inner: relay info related to the frequency of waves, through afferent fibers to the brain
  
  • Outer: play a role in the amplification of sounds and receive the info related to the location of sounds from the brain through efferent fibers

Question 29

Which is more present in the ear: inner or outer hair cells?

Answer 29

About 3x more outer hair cells

Question 30

The majority of info carried to the brain comes from? Why?

Answer 30

95% of info carries to the brain comes from inner cells - Because 90% of inner hair cells are connected to spiral ganglion cells (ganglion cells receive info from 1 hair only but 1 hair is connected to many ganglions)

Question 31

What forms the auditory nerve?

Answer 31

Axons of spiral ganglions

Question 32

How is the auditory nerve also called? 2 names

Answer 32

vestibulocochlear nerve or cranial nerve VIII

Question 33

Where does info from the auditory nerve ends up?

Answer 33

In the primary auditory cortex in the temporal lobes

Question 34

What are the 3 cochlear nuclei in the medulla to which the auditory nerve projects?

Answer 34

• Dorsal
• Anteroventral
• Posteroventral

Question 35

What does it means that the basilar membrane is tonotopically mapped?

Answer 35

high-frequency sounds processed at the base of basilar membrane are processed ventrally and low frequency sounds are processed dorsally

Question 36

From the chochlear nuclei, where is the info relayed (two pathways)?

Answer 36

to contralateral superior olivary nucleus through the brainstem (Primary pathway)
into to the ipsilateral superior olivary nucleus (Secondary pathway)

Question 37

From the superior olivary nucleus, where is the info relayed?

Answer 37

info flows through the inferior colliculus of the midbrain to the contralateral and ipsilateral medial geniculate nucleus (MGN) of the thalamus, and then to A1