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Neuro Exam 1 > Hearing > Flashcards

Hearing Flashcards

1
Q

transduction

A

taking environmental energy and converting it to neural energy

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2
Q

CN VIII - vestibulocochlear nerve

A

*2 separate nerves that travel together as one
*located in the caudal pons
*travels close to facial nerve to pass through internal auditory meatus

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3
Q

sound waves

A

vibrations cause air molecules to vibrate (compress and expand)

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4
Q

what are the 3 characteristics of sound waves that the ear must code for in order to represent differences in sounds

A

1) pitch
2) loudness
3) timing

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5
Q

pitch

A

frequency in cycles per second (Hz)

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6
Q

loudness

A

sound level in decibels (dB)

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7
Q

timing of sound

A

onset, offset, duration, and gaps

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8
Q

determining location of sound

A

*direction and distance of where a sound is coming from
*must be computed CENTRALLY, not by the ear itself

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9
Q

outer ear - structures

A

-pinna (outer fleshy part of the ear)
-auditory canal

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10
Q

function of the pinna

A

helps harness and amplify sound waves

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11
Q

functions of auditory canal

A

-carries sound waves to middle ear
-amplifies sound

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12
Q

middle ear - structures

A

-ossicles
-tympanic membrane

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13
Q

functions of ossicles

A

-malleus, incus, and stapes
*vibrate as a result of tympanic membrane vibration, hitting the oval window and causing fluid in the cochlea to vibrate

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14
Q

functions of tympanic membrane

A

-aka eardrum
*compressed air hits the TM and causes the membrane to vibrate, subsequently causing vibration of the ossicles

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15
Q

amplification in the middle ear

A

*purpose of middle ear: conduct and amplify sound
20x amplification from size differential between the tympanic membrane and the oval window

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16
Q

structures of the inner ear

A

-oval window
-cochlea

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17
Q

transmission of sound in the inner ear

A

*once the ossicles vibrate, they cause the oval window to vibrate
*vibration of the oval window causes perilymph to vibrate
*organ of Corti is where transduction occurs

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18
Q

steps in the reception and transduction of sound energy

A

1) sound waves arrive at tympanic membrane
2) displacement of auditory ossicles
3) pressure waves in the perilymph of the vestibular duct
4) pressure waves distort basilar membrane
5) vibration of hair cells against the tectorial membrane
6) information about region and intensity of stimulation relayed to CNS

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19
Q

basilar membrane

A

-the basilar membrane is the base of the organ of corti
*as sound waves pass through the endolymph of the scala vestibuli and tympani, they cause the basilar membrane to vibrate
*basilar membrane is stiff at base and loose at apex
*this causes it to create a tonotopic map on the cochlea, with:
-high frequencies at the BASE (closest to outer ear)
-low frequencies at the APEX

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20
Q

tonotopic organization of the basilar membrane

A

**base = high frequencies
**apex = low frequencies

21
Q

organ of corti & tectorial membrane

A

*tecotorial membrane is the roof of the organ of corti
*as the basilar membrane vibrates up and down, the tectorial membrane vibrates side to side
*in between the 2 membranes are HAIR CELLS

22
Q

inner hair cells of organ of corti

A

*hair cells transduce vibrations into depolarization, which leads to vesicular release that excites auditory afferent fibers and causes them to discharge
*hair cells are firmly attached to the basilar membrane, moving up and down with it as it vibrates
*as the basilar membrane moves upward, the stereocilia on top of the hair cells will BEND

23
Q

perilymph

A

*fills the scala vestibuli and scala tympani
*similar to CSF in composition

24
Q

endolymph

A

*fluid in scala media (cochlear duct)
*bathes the organ of corti
*similar to intracellular fluid and VERY RICH IN K+

25
Q

transduction by inner hair cells

A

1) upward displacement of the basilar membrane creates a shearing force that results in LATERAL DISPLACEMENT of the cilia cells
2) displacement of the cilia causes K+ INFLUX, and hair cell is depolarized
3) the depolarization causes Ca2+ entry and the fusion of vesicles, and then the release of glutamate (neurotransmitter) from hair cells
4) this causes excitation and spiking of the auditory afferent fibers

*NOTE: this is a GRADED potential, not an action potential

26
Q

tip links

A

connect tips of adjacent stereocilia to help increase the change of receptor potential

27
Q

outer hair cells

A

*helps with hearing specific sounds and amplification
*can contract, and therefore act as motor units that amplify the movement of the basilar membrane in response to a stimulus

28
Q

auditory pathways to brain

A

*after leaving the cochlear nucleus, some axons remain ipsilateral, while most decussate to the contralateral side
*therefore, the majority of auditory info processed by each half of the brain comes from the ear on the other side of the head
*both crossed and uncrossed fibers synapse in the SUPERIOR OLIVARY COMPLEX
*then, neural impulses travel to the INFERIOR COLLICULUS to the MEDIAL GENICULATE NUCLEUS and then to the AUDITORY CORTEX

29
Q

lateral lemniscus

A

pathway of auditory information traveling from the superior olive to the inferior colliculus

30
Q

tonotopic map of auditory cortex

A

*the auditory cortex has a tonotopic organization, just like the basilar membrane does

31
Q

primary auditory cortex

A

located in transverse gyri hidden in the lateral Sylvian fissure on the superior surface of the temporal lobe

32
Q

arcuate fasciculus

A

connects the primary and secondary auditory cortical areas

33
Q

secondary speech-related cortical areas

A

1) Wernicke’s sensory speech area (in parietal lobe)
2) Broca’s motor speech area (in frontal lobe)

34
Q

conductive hearing loss results from damage to what ear structures

A

*outer/middle ear
*conductive hearing loss is problems getting the sound in

35
Q

sensorineural hearing loss results from damage to what ear structures

A

inner ear, CN VIII, or CNS

36
Q

signs and symptoms of hearing loss may include

A

*muffling of speech and other sounds
*difficulty understanding spoken words, especially against background noise or in a crowd
*trouble hearing consonants
*frequently asking other to speak more slowly, clearly, and loudly
*needing to turn up the volume on TV or radio

37
Q

unilateral (monaural) hearing loss - etiology examples

A

*internal auditory artery infarct
*sudden sensorineural hearing loss
*Meniere’s disease
*vestibular schwannoma

38
Q

bilateral (binaural) hearing loss - etiology examples

A

*presbycusis
*ototoxic meds
*sequela of meningitis
*neurofibromatosis type II with bilateral vestibular schwannomas

39
Q

tinnitus

A

*ringing in the ear
*can be conductive or sensorineural

-if hair cells in the cochlea are damaged, they may move randomly, causing tinnitus
-can also be caused by turbulence in the carotid artery or jugular vein

40
Q

examples of conduction deafness

A

1) obstruction (either foreign body or congenital malformation)
2) otosclerosis
3) otitis media
4) cholesteatoma

41
Q

otosclerosis

A

*overgrowth of bone (usually near stapes)
*causes conductive hearing loss

42
Q

otitis media

A

*most common cause of conductive hearing loss
*begins with an ordinary URI involving the nasopharynx
*nasal secretions infect the eustachian tube
*eustachian tube becomes inflamed and can no longer equalize pressure, causing bulging of the tympanic memrane

43
Q

cholesteatoma

A

*abnormal, noncancerous skin growth that can develop in the middle section of your ear, behind the eardrum
*often develops a cyst or sac that sheds layers of old skin
*causes conductive hearing loss

44
Q

examples of sensorineural deafness

A

1) presbycusis
2) noise-induced
3) acoustic neuroma
4) meniere’s disease

45
Q

prebycusis

A

*age-related hearing loss
*consequence of gradual hair cell lost, first in the base (high frequency representation) of the cochlea
*causes sensorineural hearing loss
*most common cause of hearing loss overall

46
Q

noise-induced hair cell loss

A

*causes sensorineural hearing loss
*mostly from noise > 90 dB

47
Q

acoustic neuroma/vestibular schwannoma

A

*most common tumor of the cerebellopontine angle
*takes up space and compresses CN VIII
*benign
*arises from the vestibular portion of the eighth cranial nerve when schwann cells start to proliferate
*causes sensorineural hearing loss

48
Q

rinne test

A

*test for hearing loss
*strike tuning fork, then put it behind pinna until you can no longer hear it, then put it next to the ear and you should still be able to hear it

49
Q

weber test

A

*test for hearing loss
*strike tuning fork and place on top of the head
*should hear it the same on both sides

Neuro Exam 1 (22 decks)

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