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Flashcards in Hearing Deck (78)
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1
Q

What functional nerve component is the hearing system?

A

Special Somatic Afferent

2
Q

What is meant by the pitch of a sound?

A

Its frequency

3
Q

What frequencies can the human ear hear?

A

20 - 20k

4
Q

At what frequencies is the ear most sensitive to?

A

2k - 4k

5
Q

What is the frequency of a normal human voice?

A

500 - 2k

6
Q

What frequencies are vowels and bass sounds?

A

Low

7
Q

What frequencies are consonants and treble sounds?

A

High

8
Q

What is loudness of sound a function of?

A

Amplitude (db)

9
Q

What decibels can humans hear?

A

1 - 120 db

10
Q

Above what db is sound damaging to the human ear?

A

100 db

11
Q

Above what db can sound not be heard?

A

120 db

12
Q

What are the 2 portions of the external ear?

A
  • Pinna (auricula) that acts as a funnel, channeling airborne sound into ear
  • Auditory canal
13
Q

How large is the opening of the auditory canal?

A

2.5 cm

14
Q

What is the function of the middle ear?

A

Converts air sound waves into fluid waves

15
Q

What are the 5 components of the anatomy of the inner ear?

A
  • Tympanic membrane
  • Ossicles
  • Malleus
  • Incus
  • Stapes (stirrup)
16
Q

How is the tympanic membrane shaped?

A
  • Conical with the pointed end projecting into the cavity
17
Q

What is the function of the ossicles?

A

Sound amplification

18
Q

What is the function of the malleus?

A

Hammer (connects rigid to incus)

19
Q

What is the function of the incus?

A

Anvil (connects flexible with stapes)

20
Q

What is the function of the stapes?

A
  • Stirrup (Flat bottom/ footplate) that moves in and out like a piston
21
Q

How does the middle change with altitude?

A
  • Expands at high altitudes

- Condenses at low altitudes

22
Q

How can the auditory tubes be used when adjusting to altitudes?

A
  • Connect middle ear to oropharynx
  • Can move air in at lower altitudes
  • Can move air out at high altitudes
23
Q

Why do children have more ear infections than adults?

A

They do not clear the middle ear as well

24
Q

What are the 2 ways that bone amplifies air waves?

A
  • Force
  • Surface area (tympanic membrane is larger than membrane of oval window; lever system of ossicles increases mechanical advantage)
25
Q

What are the 2 muscles associated with the inner ear?

A
  • Tensor tympani

- Stapedius

26
Q

What structure does the tensor tympani insert into?

A

The malleus

27
Q

What is the function of the tensor tympani?

A

Decrease amount of movement of the ear drum

28
Q

What nerve innervates the tensor tympani?

A

CN V

29
Q

What is the function of the stapedius?

A

Restricts movement of the footplate of the stapes against the oval window

30
Q

What nerve innervates the stapedius?

A

CN VII

31
Q

How do the muscles protect the ears?

A

Prevent the bone and membranes from moving as much

32
Q

How fast the attenuation reflex produced by the stapedius and tensor tympani?

A

50 - 100 ms

33
Q

What is the shape of the canal of the cochlea?

A
  • Spiral
34
Q

How many turns does the cochlea make? How long is it? What is its diameter?

A

2.5 turns
32mm long
2 mm diameter

35
Q

What divides the bony labyrinth into 2 portions? What are the 2 portions?

A

Cochlear partition divides:

  • Scala vestibuli
  • Scala tympani
36
Q

What is contained within the cochlear partition?

A

Cochlear duct

37
Q

What are the 2 membranes of the cochlear partition?

A
  • Vestibular membrane/ Reissner’s membrane

- Basilar membrane

38
Q

What do the 2 membranes of the cochlear partition separate?

A
  • Endolymph filled cochlear duct from perilymph filled with scala vestibuli and scala tympani
39
Q

What is the name of the apex of the duct?

A

Helicotrema

40
Q

Where is the basilar membrane wider?

A

At apex (5X greater than base)

41
Q

Where is the basilar membrane tension greater?

A

100x stiffer at base than apex

42
Q

What occurs in the basilar membrane with a high frequency sound?

A

Base will vibrate dissipating most of the nergy and the wave will not propogate

43
Q

What occurs in the basilar membrane with a low frequency sound?

A

Waves travel to apex before energy dissipates

44
Q

What is stimulated by movement of the basilar membrane?

A

Hair cells of organ of corti

45
Q

Is the oval window an entrance or exit?

A

Entrance

46
Q

Is the round window an entrance or exit?

A

Exit

47
Q

What is the order of canals through which a propogated sound travels through?

A

Scala vestibuli
Helicotrema
Scala tympani

48
Q

What window creates the fluid waves that bend the basilar membrane?

A

Oval window

49
Q

Where is the organ of corti found?

A

Longitudinally along the length of the basilar membrane

50
Q

What is the organ of corti?

A

A transducer

51
Q

Where are the hair cells of the organ of corti located?

A

Sandwiched between basilar membrane and reticular lamina

52
Q

What membrane do the hair cells extend into?

A

The tectoral membrane

53
Q

How do fluid waves cause depolarization of hair cells?

A
  • Waves move basilar membrane, moving entire unit, bending hair cells as the unit moves up towards the tectoral membrane
  • Bending of hair cells causes depolarization
54
Q

What are the 2 types of hair cells?

A

Inner and outer

55
Q

How many outer hair cells are there to one inner?

A

3

56
Q

What type of cells communicate with outer hair cells?

A

Spiral ganglion

57
Q

What is the roll of the spiral ganglion of the auditory nerve in the organ of corti?

A

Selection of attention

58
Q

What type of neuron cell types are found in the auditory nerve spiral ganglion?

A

Bipolar

59
Q

Toward what structure is the basilar membrane stiffer?

A

Basilar window

60
Q

Toward what structure is the basilar membrane less stiff/ wider?

A

Toward helicotrema

61
Q

How can inner hair cells help dampen sound?

A
  • 95 % go out sensory nerve, but 5 % go to outer hair cells to stiffen the comlex
62
Q

Are higher frequency sounds processed in the anterior or posterior cochlear nucleus? Low frequency sounds?

A

High frequency: Posterior

Low frequency: Anterior

63
Q

What fibers ascend to higher centers?

A

Auditory fibers to perceive sound

64
Q

Describe the pathway of cochlear nerve fibers from the spiral ganglion to higher centers.

A
  • Enter through cochlear nerve, and synapse on dorsal cochlear nucleus
  • Ascend and some fibers cross at trapezoid body onto superior olive
  • Fibers ascend as LATERAL LEMNISCUS
  • Synapse on nucleus of lateral lemniscus
  • Some fibers cross over
  • Synapse on inferior colliculus
  • Some fibers cross over
  • Fibers synapse on medial geniculate body
  • Synapse on sublenticular fasciculus and auditory thalamocortical radiation
65
Q

How is low frequency sound localized on the horizontal plane?

A

Interaural time delay

  • Difference in sound between 2 ears
  • High frequency sound doesn’t work because 1 cycle of sound is smaller than the distance between the ears
66
Q

How is high frequency sound localized in the horizontal plane?

A

Interaural intensity differences

  • Head casts a sound shadow that dampens the sound on the side blocked by the head
  • Low frequency diffracts around head, eliminating this effect
67
Q

How are sounds localized in the vertical plane?

A
  • Bumps and ridges of pinna produce reflections of entering sounds
  • The delay between direct and indirect paths cause sound delays
68
Q

What is the function of olivocochlear efferent reflexes?

A
  • Selective tuning
  • Focusing
  • Possibly protection
69
Q

What is the function of somatic motor auditory reflexes?

A
  • Contracts ear muscle during loud sounds

- Start responses

70
Q

What tract processes startle responses?

A

Tectospinal tracts

71
Q

What is conduction deafness?

A
  • Interference with passage of sound waves through external or middle ears
72
Q

What is nerve deafness?

A
  • Damage to receptor cells of spiral organ or the cochlear nerve
  • Damage to organ of cordi/ afferent fibers
  • Can occur in both directions
73
Q

Which type of hearing loss is NEVER complete or total?

A

Conduction deafness

74
Q

What determines the amount of deafness due to nerve deafness?

A

Amount of damage

75
Q

When are high frequencies typically lost?

A

In older populations

76
Q

What sounds are most damaging when individuals are young?

A

Low bass

77
Q

What is Weber’s test?

A
  • 256 Hz tuning fork placed on themidline of the head
  • If the patient hears it normally in both ears, then this is normal
    Conduction deafness: Sound localized in decreased hearing ear
    Nerve deafness: Sound localized in unaffected ear
78
Q

What is Rinne’s test?

A
  • 512 Hz tuning fork placed on mastoid process
  • Place it nera ear and hold until it can’t be heard
    Normal: Air conduction is louder than vibration