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Flashcards in Hearing Deck (78):
1

What functional nerve component is the hearing system?

Special Somatic Afferent

2

What is meant by the pitch of a sound?

Its frequency

3

What frequencies can the human ear hear?

20 - 20k

4

At what frequencies is the ear most sensitive to?

2k - 4k

5

What is the frequency of a normal human voice?

500 - 2k

6

What frequencies are vowels and bass sounds?

Low

7

What frequencies are consonants and treble sounds?

High

8

What is loudness of sound a function of?

Amplitude (db)

9

What decibels can humans hear?

1 - 120 db

10

Above what db is sound damaging to the human ear?

100 db

11

Above what db can sound not be heard?

120 db

12

What are the 2 portions of the external ear?

- Pinna (auricula) that acts as a funnel, channeling airborne sound into ear
- Auditory canal

13

How large is the opening of the auditory canal?

2.5 cm

14

What is the function of the middle ear?

Converts air sound waves into fluid waves

15

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

- Tympanic membrane
- Ossicles
- Malleus
- Incus
- Stapes (stirrup)

16

How is the tympanic membrane shaped?

- Conical with the pointed end projecting into the cavity

17

What is the function of the ossicles?

Sound amplification

18

What is the function of the malleus?

Hammer (connects rigid to incus)

19

What is the function of the incus?

Anvil (connects flexible with stapes)

20

What is the function of the stapes?

- Stirrup (Flat bottom/ footplate) that moves in and out like a piston

21

How does the middle change with altitude?

- Expands at high altitudes
- Condenses at low altitudes

22

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

- Connect middle ear to oropharynx
- Can move air in at lower altitudes
- Can move air out at high altitudes

23

Why do children have more ear infections than adults?

They do not clear the middle ear as well

24

What are the 2 ways that bone amplifies air waves?

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

25

What are the 2 muscles associated with the inner ear?

- Tensor tympani
- Stapedius

26

What structure does the tensor tympani insert into?

The malleus

27

What is the function of the tensor tympani?

Decrease amount of movement of the ear drum

28

What nerve innervates the tensor tympani?

CN V

29

What is the function of the stapedius?

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

30

What nerve innervates the stapedius?

CN VII

31

How do the muscles protect the ears?

Prevent the bone and membranes from moving as much

32

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

50 - 100 ms

33

What is the shape of the canal of the cochlea?

- Spiral

34

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

2.5 turns
32mm long
2 mm diameter

35

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

Cochlear partition divides:
- Scala vestibuli
- Scala tympani

36

What is contained within the cochlear partition?

Cochlear duct

37

What are the 2 membranes of the cochlear partition?

- Vestibular membrane/ Reissner's membrane
- Basilar membrane

38

What do the 2 membranes of the cochlear partition separate?

- Endolymph filled cochlear duct from perilymph filled with scala vestibuli and scala tympani

39

What is the name of the apex of the duct?

Helicotrema

40

Where is the basilar membrane wider?

At apex (5X greater than base)

41

Where is the basilar membrane tension greater?

100x stiffer at base than apex

42

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

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

43

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

Waves travel to apex before energy dissipates

44

What is stimulated by movement of the basilar membrane?

Hair cells of organ of corti

45

Is the oval window an entrance or exit?

Entrance

46

Is the round window an entrance or exit?

Exit

47

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

Scala vestibuli
Helicotrema
Scala tympani

48

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

Oval window

49

Where is the organ of corti found?

Longitudinally along the length of the basilar membrane

50

What is the organ of corti?

A transducer

51

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

Sandwiched between basilar membrane and reticular lamina

52

What membrane do the hair cells extend into?

The tectoral membrane

53

How do fluid waves cause depolarization of hair cells?

- 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

What are the 2 types of hair cells?

Inner and outer

55

How many outer hair cells are there to one inner?

3

56

What type of cells communicate with outer hair cells?

Spiral ganglion

57

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

Selection of attention

58

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

Bipolar

59

Toward what structure is the basilar membrane stiffer?

Basilar window

60

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

Toward helicotrema

61

How can inner hair cells help dampen sound?

- 95 % go out sensory nerve, but 5 % go to outer hair cells to stiffen the comlex

62

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

High frequency: Posterior
Low frequency: Anterior

63

What fibers ascend to higher centers?

Auditory fibers to perceive sound

64

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

- 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

How is low frequency sound localized on the horizontal plane?

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

How is high frequency sound localized in the horizontal plane?

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

How are sounds localized in the vertical plane?

- Bumps and ridges of pinna produce reflections of entering sounds
- The delay between direct and indirect paths cause sound delays

68

What is the function of olivocochlear efferent reflexes?

- Selective tuning
- Focusing
- Possibly protection

69

What is the function of somatic motor auditory reflexes?

- Contracts ear muscle during loud sounds
- Start responses

70

What tract processes startle responses?

Tectospinal tracts

71

What is conduction deafness?

- Interference with passage of sound waves through external or middle ears

72

What is nerve deafness?

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

73

Which type of hearing loss is NEVER complete or total?

Conduction deafness

74

What determines the amount of deafness due to nerve deafness?

Amount of damage

75

When are high frequencies typically lost?

In older populations

76

What sounds are most damaging when individuals are young?

Low bass

77

What is Weber's test?

- 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

What is Rinne's test?

- 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