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Y1 - Neuroanatomy - Exam 2 > 3. Auditory System > Flashcards

3. Auditory System Flashcards

1
Q

external ear:

function and components

A
  • fxn: collect and transmit sounds
  • components
    • auricle: outer ear; shape to collect sound
    • external auditory meatus: transmitting sound
    • tympanic membrane: transform sound wave to mechanical vibration
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2
Q

middle ear:

fxn and components

A
  • fxn: transmit and amplify sound signal
  • components:
    • malleus, incus, stapes
    • middle ear cavity
    • oval window
    • round window
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3
Q

inner ear:

function and components

A
  • fxn: transforms sound to electric signals
  • components:
    • scala vestibuli
    • scala tympani
    • cochlea duct or scala media
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4
Q

which 2 small mucles are important in protecting the ear?

A
  • Tensor tympani muscle: innervated by trigeminal nerve (CN V)
  • Stapedius muscle: connected to stapes; inn. by facial nerve
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5
Q

malleus, incus, and stapes correspond with which shapes?

A
  • malleus = hammer
  • incus = anvil
  • stapes = stirrups
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6
Q

which inner ear structure contains perilymph?

contents of perilymph?

A
  • scala vestibuli
  • low potassium, high sodium (similar to ECF)
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7
Q

which inner ear structure contains endolymph?

contents of endolymph?

A
  • cochlear duct/ or scala media
  • high potassium, low sodium
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8
Q

where is the helicotrema found?

A

at the apex of the cochlea (curling structure)

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9
Q

which type of hair cells receive the majority of spiral ganglion innervation?

A
  • 90% of spiral ganglion innervate Inner hair cell; as many as 20 spiral ganglion per 1 inner hair cell
  • whereas only 10% of spiral ganglion innervate the 3 outer hair cells; 1 spiral ganglion can cover 12 outer hair cells
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10
Q

what supports hair cells? what is the function?

A

hair cells are supported by phalangeal (supportive) cells –>

which act to “stiffen” the superior surface of the organ of corti

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11
Q

where are the 1st order neurons in audition?

A

cell bodies in the modiolus (spiral ganglion neurons);

cell body is in the cochlea –> sends the process to the hair cells

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12
Q

process of inhibition of hair cells

A
  1. stereocilia is deflected AWAY from longer stereocilia
  2. hair membrane depolarizes
  3. afferent nerve fibers are not stimulated
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13
Q

mechanism for excitation of hair cells?

A
  • stereocilia deflected TOWARDS the longer stereocilia
  • results in influx of K+ ions
  • hair cell membrane depolarizes
  • influx of calcium ions
  • then NTs are released –>
  • afferent nerve fibers are stimulated (excitation)
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14
Q

where is there tonotopic localization?

A

in organ of corti

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15
Q

which type of frequency sounds are found at the helicotrema?

A

lower frequency tones

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16
Q

which type of frequency sounds are found at the base/ closer to middle ear?

A

high frequency sounds

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17
Q

what movement causes the difference in sound frequencies?

how?

A

the basilar membrane oscillation allows for diff’t frequencies;

  • the base (closer to middle ear) is more stiff/narrow, so higher frequency oscillations will occur here
  • whereas the apex/helicotrema is floppy/wide/elastic –> lower frequency stimulation/tone
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18
Q

path of axons from hair cells?

A
  • hair cell axons that are excited –>
  • travel from spiral ganglion –>
  • via cranial nerve 8 (vestibulocochlear) –>
  • to cochlear nucleu –>across midline to
  • superior olivary nucleus –> ascends to inferior colliculus –>
  • via brachium of inf. colliculus –> medial geniculate nucleus —>
  • via auditory radiation –>
  • to transverse temporal gyrus of heschi
  • into the medulla
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19
Q

where are the cochlear nuclei found?

A

cochlear division (CN VIII)

the dorsal & ventral cochlear nuclei are found in the medulla

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20
Q

where do cochlear axons synapse?

A

on the ventral and dorsal cochlear nuclei

w/in the medulla

21
Q

CC: sxs of lesion of nerve or cochlear nuclei?

A

deafness

22
Q

in coronal section, which cochlear nuclei is more inferolateral?

also identify where 4th ventricle would be

A

ventral nuclei

4th ventricle is medial, empty white space

23
Q

why would there not be deafness with a unilateral lesion above the cochlear nuclei?

A

there are a lot of bilateral projections above the cochlear nuclei –>

so it would be able to compensate

24
Q

where do the cochlear nuclei travel to as they ascend?

A

to the caudal pons;

specifically the:

  • Superior olivary nucleus FIRST
  • Lateral lemniscus –> fibers to LL ascend from SON
  • Trapezoid body –> fibers from SON decussate/cross over midline through trapezoid body
25
Q

would a unilateral lesion in the Lateral Lemniscus, Trapezoid body, or Superior olivary nuceli cause deafness?

A

no, bc there are bilateral projections at multiple sites in the brainstem

26
Q

How do auditory axons travel from the superior olivary nucleus?

A

can travel via lateral lemniscus –>

  • either continue ascending the brainstem thru cerebral crus to the inferior collilulus, OR
  • synapse at nucleus of lateral lemniscus, and travel across the commissure of lateral lemniscus –> caudal mibdbrain
27
Q

describe pathway from midbrain to thalamus?

A

the interior colliculus of the caudal midbrain –>

to the medial geniculate nucleus in the thalamus

28
Q

where does the medial geniculate nucleus of the thalamus project to?

A

the primary auditory cortex

(aka transverse temporal gyri)

29
Q

describe the tonotopic organization of the auditory cortex?

A
  • medial side of auditory cortex = high frequency sounds (base)
  • lateral side of auditory cortex = low frequency sounds (apex/helicotrema)
30
Q

where are low frequency sounds found

(w/ regards to tonotopic organization)

A

lateral side of auditory cortex = low frequency sounds from the apex/helicotrema

31
Q

which gyri contain the primary auditory cortex?

A

transverse temporal gyri;

information from here goes to unimodal –> then heteromodal association cortex

32
Q

tone:

define

A

frequency; can be high or low

33
Q

what affects how loud or quiet a sound is?

A

the amplitude of sound;

i.e. differential firing of afferent fibers

34
Q

where does sound localization occur?

what does it require?

A

occurs in superior olive nucleus

requires information from both ears to be able to localize the sound

35
Q

where do unilateral lesions occur to produce hearing loss?

A

*but not higher than the cochlear nuclei

  • cochlear nuclei
  • CN 8 (vestibulocochlear nerve)
  • cochlea
36
Q

a unilateral lesion in the pons, midbrain, or cortex would not produce deafness — why?

A

due to bilateral projections at multiple sites in the brainstem

37
Q

superior olivary nuclei:

pathway and function

A
  • project back to cochlea to inhibit auditory nerve terminals on hair cells
  • regulates hair cell sensitivity –> regulating selective attention to certain sounds by affecting olivococlear efferent fibers
38
Q

conductive hearing loss:

define, and possible causes

A
  • (sound transmission is the problem; issue w/ outer or middle ear, or TM)
  • causes incl:
    • foreign bodies in external acoustic meatus
    • perforated tympanic membrane
    • otitis media
    • otosclerosis
    • cholesteatoma
39
Q

otosclerosis:

define

A

overgrowth of bones around stapes; if bones are stuck, we can’t hear

40
Q

cholesteatoma:

define

A

overgrowth of desquamated keratin debris w/in middle ear cavity;

preventing sound transmission

41
Q

sensorineual hearing loss:

define and causes

A
  • in which the root cause lies in the inner ear or sensory organ (cochlea and associated structures) or the vestibulocochlear nerve (cranial nerve VIII)
  • causes incl:
    • congenital hearing loss -genetic mutations, developmental insults
    • acquired hearing loss
    • noise-induced hearing loss
    • aging-related hearing loss
    • lesions in auditory pathway
42
Q

noise-induced hearing loss:

define

A

types of hearing loss damage to
sterociliated cells in organ of corti, loss of high frequency hearing first

43
Q

Aging related progressive bilateral/symmetric sensorineural
hearing loss:

define

A

often of higher frequencies due to the destruction of
hair cells at the cochlear base.

44
Q

which 2 tests can be used to distinguish conductive vs. sensory neural hearing loss

A
  • Rinne: air conduction –>and then placing on temporal bone to see if you hear the sound through the bone conduction
  • Weber: place tuning fork on midline of forehead; sound is conducted through temporal bone; ask where they hear the sound,
45
Q

bone conduction:

define

A

Sound vibration can be transmitted through temporal bone vibration to inner ear, less effective than air conduction

46
Q

air conduction:

define

A

Sound transmission through tympanic membrane vibration and ossicle movement, more effective than bone conduction

47
Q

which is more effective?

air or bone conduction?

A

air conduction

48
Q

results of weber and rinne tests for:

conductive hearing loss

A
  • Weber: localizes to AFFECTED ear
  • Rinne: abnormal (BC > AC)
49
Q

results of Weber and Rinne tests for:

sensory neural hearing loss

A
  • Weber: localizes to UNAFFECTED ear
  • Rinne: normal (BC < AC), w/ AC being more effective

Y1 - Neuroanatomy - Exam 2 (12 decks)

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