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LAST NEURO EVER > AV > Flashcards

AV Flashcards

1
Q

What are the two functions of CN VIII?

A

cochlear: sound
vestibular: head position and mvmt

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2
Q

Where are the semicircular canals located?

A

attached the vestibule

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3
Q

What are the two main divisions of the inner ear?

A

vestibule (semicircular canals) and cochlea (swirly thing)

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4
Q

What are the two enlargements of the membranous labyrinth in the vestibule?

A

utricle – semicircular canals attached here

saccule – connects cochlear duct and utricle

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5
Q

Where would you find perilymph?

A

fills the bony labyrinth

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6
Q

Where would you find endolymph?

A

fills membranous labyrinth

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7
Q

What keeps perilymph and endolymph from mixing?

A

tight junctions in hair cells

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8
Q

What are the causes and symptoms of Meneiere’s disease?

A

causes: not sure why but swelling of membranous labyrinth fucks with the endolymph
symptoms: vertigo, nausea, tinnitus

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9
Q

Describe a hair cell.

A

polarized cell: has specialized stereocilia on the top, connections to CN VIII on bottom

tallest of the stereocilia (called kinocilium) is embedded in a gelatinous structure, who’s name and components change based on where the hair cell is located

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10
Q

Do cochlear hair cells have kinocilia?

A

no

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11
Q

Where are hair cells with kinocilia located?

A

semicircular ducts, utricle, saccule

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12
Q

Hair cells in the organ of corti

part of labyrinth?
gelatinous material?
stimulus transmitted?

A

part of labyrinth: cochlea
gelatinous material: tectorial membrane
stimulus: sound

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13
Q

Hair cells in the cristae

part of labyrinth?
gelatinous material?
stimulus transmitted?

A

part of labyrinth: semicircular ducts
gelatinous material: cupula
stimulus: angular acceleration

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14
Q

Hair cells in the maculae

part of labyrinth?
gelatinous material?
stimulus transmitted?

A

part of labyrinth: utricle, saccule
gelatinous material: otolithic membrane
stimulus: linear acceleration

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15
Q

How do hair cells work?

A

all use same basic mechanism: deflection of stereocilia initiated by gelatinous material causes action potential

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16
Q

What happens if there is deflection towards the tallest stereocilia?

A

cell depolarized (action potential)

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17
Q

What happens if there is deflection away from the tallest stereocilia?

A

cell is hyper polarized (no action potential)

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18
Q

What happens if there is deflection perpendicular to the tallest stereocilia?

A

nothing

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19
Q

When the stapes strikes the round window, is endolymph or perilymph directly affected?

A

perilymph, because perilymph is in the bony labyrinth

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20
Q

What is the function and innervation of the stapedius muscle

A

pulls stapes away from oval window of cochlea (blocks sound of own voice)

CN VII

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21
Q

What is the function and innervation of the tensor tympani muscle

A

pulls malleus in toward middle ear (adding tension to tympanic membrane (blocks chewing sounds)

CN V

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22
Q

What are the three channels of the cochlea?

A

scala vestibuli
scala media
scala tympani

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23
Q

Whats inside the scala vestibuli, and what is it continuous with?

A

filled with perilymph

continuous with vestibule

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24
Q

Whats inside the scala media?

A

endolymph, spiral organ of corti

25
Q

Whats inside the scala tympani and what is it continuous with?

A

filled with perilymph

ends blindly at round window

26
Q

Where are the primary afferent fibers of cochlear division of CN VIII?

A

inside the modiolus (spongy bone at center of cochlea)

27
Q

How does the spiral organ of corti work?

A

has inner hair cells and outer hair cells

inner hair cells are stimulated by endolymph mvmt

outer hair cells are stimulated by vibrations of the basilar membrane (which is what the SOC lies on)

28
Q

What is the path of vibrations as the enter the cochlea?

A
  1. vibrations begin as stapes hits the oval window
  2. vibrations travel through perilymph in the scala vestibule
  3. vibrations pass through the scala media (cochlear duct)/endolymph and stimulate the spiral organ of corti
  4. vibrations continue through the perilymph of the scala tympani, where they end blindly at the round window
29
Q

How is the auditory system tonotopically arranged?

A

different parts of the basilar membrane are stimulated by different tones

the different tones are sent to specific relax nuclei and cortex

30
Q

Would a cochlear implant help someone who’s CN VIII endings are destroyed?

A

no, it only helps those who have intact nerve endings but dead hair cells

31
Q

What is the primary ascending auditory pathway and is it contra, ipsi or bilateral?

A

lateral lemniscus

bilateral (info from both ears)

mostly info from dorsal cochlear nucleus

32
Q

What is the auditory relay nuclei of the thalamus?

A

MGN

33
Q

If you have a stroke in your brainstem, are you likely to become totally deaf?

A

no because the auditory pathway is very bilateral

34
Q

How does auditory info get from the inferior colliculus to the MGN?

A

inferior brachium

35
Q

Where is the primary auditory cortex located?

A

transverse temporal gyrus of Heschl

superior surface of temporal lobe

36
Q

How does the CNS locate where sound is coming from?

A

sound from the left would reach left ear first (compare arrival times)

superior olivary nucleus important to sound localization

37
Q

What does the superior olivary nucleus do and how

A

compares arrival times

info enters from both cochlear nuclei, crossing milline at trapezoid body

medial sub nuclei of superior olivary nucleus compares times, who the fuck knows what the lateral sub nuclei is doing

38
Q

What is the role of the vestibular division of CN VIII?

A

detect linear and angular acceleration of head

regulate posture, coordinate head and eye mvnts

39
Q

Where are cristae located?

A

at the end of each semicircular duct, there is an ampules (thickening) and the cristae is located here (cristae is just a ridge with hair cells)

40
Q

Where is the cupula located?

A

kind of sits like a really tall hat on top of the cristae (like an upwards extension of cristae), extends across the ampulla

41
Q

How does the cupula work?

A
  • the semicircular duct rotates in a perpendicular direction the cupula
  • if you rate the duct to the right, the endolymph inside the duct will travel the opposite way due to inertia
  • if the stereocilia located in the cupula are bent towards the tallest stereocilia, an AP will be recorded

(each channel responds to changes of speed in a given plan)

42
Q

What is a macula?

A

a patch of hair cells located in the utricle and saccule

43
Q

In the utricle, which way do the macula face when the head is upright?

A

macula is horizontal

stereocilia are facing up

44
Q

In the saccule, which way do the macula face when the head is upright?

A

macula is vertical

stereocilia are facing laterally

45
Q

What type of movement do the hair cells in the utricle detect?

A

forward and backward

side to side

46
Q

What type of movement do the hair cells in the saccule detect?

A

forward and backward

up and down

47
Q

What is the otolithic membrane?

A

gelatinous membrane of macula

has crystals to increase its density

48
Q

Where do the vestibular primary afferent cell bodies project to?

A

vestibular nuclei of rostral medulla, caudal pons

some to cerebellum via juxtaform body

49
Q

Where do the vestibular nuclei get inputs from?

A

each of the semicircular ducts

cerebellum, spinal cord, contralateral vestibular nuclei

50
Q

Where do the vestibular nuclei of the brainstem project to?

A

spinal cord

CN III, IV, VI (eye movements)

contralateral vestibular nuclei

thalamus (VPL)

visceral nuclei of brainstem (adjust cardiovascular system for laying down/sitting up, sea sickness)

51
Q

What does the lateral vestibulospinal tract do?

A

excitatory projections to ipsilateral antigravity muscles (changes posture in response to tilting)

spin around on a baseball bat? you’ve just over excited your LVST congrats

52
Q

What does the medial vestibulospinal tract do?

A

extends to cervical cord via the MLF

stabilizes head mvmts as we walk, coordinates head and eye mvmts

53
Q

Describe the vestibuloocular reflex (VOR)

A

afferent limb: VIII (vestibular division)

efferent limb: III, IV, VI (eye mvmt)

has connections with MLF and reticular formation

purpose is to keep retina focused on object while you are moving

54
Q

How does your VOR work if you spin to the left while looking at something?

A
  • your left semicircular duct gets excited (CN VIII)
  • right lateral rectus muscles and left medial rectus muscles contract to keep you looking to to the right
  • your left lateral rectus and right medial rectus are inhibited
55
Q

What is nystagmus?

A

rapid back and forth eye movements

56
Q

Why does drinking alcohol give you nystagmus?

A

alcohol increases and decreases the density of your endolymph, making your semicircular canals sensitive to gravity

57
Q

What are the three things that give you positional sense?

A

vestibular
proprioceptive from spinal cord
visual systems

58
Q

What does romberg’s sign test?

romberg: ask pt to close eyes, see if they sway

A

tests whether your proprioception from spinal cord is intact

LAST NEURO EVER (5 decks)

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