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Neuro Quiz 2_yl > vestibular system > Flashcards

vestibular system Flashcards

1
Q

What are the canals in the bony labyrinth?

A

semicriculat canals, vestibules, and cochlea. The canal connecting to the outside is vestibular aqueduct.

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2
Q

What are the membranous labyrinth?

A

semicircular duct, utricle + saccule, and cochlear duct. The vestibular aqueduct is filled with endolymphatic duct and sac.

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3
Q

What filled the membranous labyrinth?

A

Endolymph

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4
Q

Where is the endolymph made?

A

strae vescularsi in teh cochlea

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5
Q

How is endolymph different from other fluid (perilymph, CSF)?

A

Lots more K; +80mV compared to perilymph

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6
Q

What is the gradient between the hair cell and the endolymph?

A

endolymph +, hair cell is negatively charged.

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7
Q

How are the two K flows?

A
  • Rapid K in flow from endolymph

- Passtive K outflow at base of harid cells into perilymph - rapid repolarization

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8
Q

What happens when vibration/mechanical force opens the K channel on tip of the stereocilia?

A

K channal opens and K flushes in, causing the hair cell to depolarize
-however these K is leaky, constitutively open

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9
Q

What are the Ca channels at the base of the hair cells?

A
  • There is voltage-dependent Ca channel, which allows Ca to come in during deplorization - help with vesicle’s release of neurotransmisstor
  • Ca also helps an Ca-dependent K channel, which allows K to go out.
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10
Q

Which direction the stereocilia needs to bend in order to fire AP?

A

Towards the kilocilium -> tension on the tip filament -> K in -> depolarization

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11
Q

What does tip links connect to?

A

Anchor in K channel, the other on a transmembrane motor protein on the side of neiboring steoreocilium (motor protein walks along actin filament)

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12
Q

Where are the hair cells?

A
  • macula (applied to the wall)
  • utricle
  • saccula
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13
Q

What is macula?

A
  • exists in utricule and sacculus
  • Hair cells attached to the wall embedded ina gel
  • the gal has otolith -calcium carbonate cystals, which increases the density of the gel - alooing the macular to respond to gravity.
  • hari cells are polarized in different directison depending on their locations (striola)
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14
Q

Where is crtistae located?

A
  • located in ampulla of semicircular duct

- all hair cells signal in one direction

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15
Q

What is the function of the maccula?

A

Detect linear acceleration and position in relation to gravity.

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16
Q

Benign positional vertigo

A

-caused by loose otoconia

17
Q

Why difficult to know the direction during diving? Or pilot lost tract of gravity when flying through a cloud

A
  • when the visual information conflicts with vestibular, we often use visual information.
  • slow movement are easily adapted
18
Q

When head tilt how the AP changes?

A

One direction - AP increases frequency;

another direction -decreases discharge rate

19
Q

What about Christae?

A
  • located in the ampula of semicircular ducts
  • the cilia protrudes into the tall cubula.
  • kilocilium is on the same side of the hair cells.
20
Q

What does Christae detect?

A
  • There are three, perpendicular to each other
  • detecting the angular acceleration.
  • think about fluid in the holu loop, inertia.
21
Q

What about the orientation of the three canals?

A
  • one canal in each ear is parallel to the other ear

- names: L and R - horizontal, anterior, and posterior

22
Q

If head tilt to one direction, what happens next?

A
  • Endolymph moves to the other direction -> cupula displacement in the ampula
  • increasing firing on one side and decreasing firing on the other side (each of the inner ear can complete the task)
23
Q

What is the semicircular canal’s innervation?

A

Terminal branches of the vestibular branch of CN VIII. Each maculae and christae has one branch innervating.

24
Q

What is the ganglion located at the end of internal acoustic meatus?

A

vestbular ganglion (Scarpa’s ganglion), where the cell bodies are, are sensory neurons: bipolar in this case

25
Q

Where is the first order neuron projecting to?

A

vestibular nuclei and to the flocculus and nodulus (vestibulocerebellum)

26
Q

Where is the fibers from cristaae going to?

A

lateral, medial and superior vestibular nuclei

27
Q

Where is the vestibular trigone?

A

Lateral to the sulcus limitans; very lateral in the brainstem (sensory!)

28
Q

Where do the vestibular nuclei receive input besides direct vestibular input?

A
  • cerebellum: mostl the flocculus and gastigial nucleus

- Spinal cord: incorporating proprioception from the body (esp from the upper neck)

29
Q

What does the input of the cerebellum do with the vestibular system?

A
  • Adjust the gain of the vestibular system
  • Reciprocal connections with the flocculonodular lobe of the cerebellum
  • These connections are critical to the ability to change gain of the VOR and adaptation of vestibular responses.
30
Q

Motion sickness

A

-adjusted by the cerebellum - adaptation

31
Q

What is the most important output for vestibular information?

A
  • adjusting the eye movement via the vestibulo-ocular reflex
  • projection through MLF, connects to nuclei (e.g. abducent, oculomotor)
  • stabilize the eye on the target when head is moving
32
Q

What underlines the vestibulocervical and vestibulospinal (righting) reflexes?

A

projection from medial and lateral vestobular nuclei to spinal cord (e.g. holding a baby in hand -> title towards the other side -> baby’s extensor muscles on the turning side will be activated to trying to maintaining the balance (in adult, this primitive reflex is suppressed)

33
Q

What carries the vestibular information?

A

Thalamocortical pathway

34
Q

What is the physiological nastagmus?

A
  • Head rotates to one side - imbalance of input on two sides
  • fast eye movement: vestibular-ocular reflex, drives the eye opposite to the direction of head movement
  • slow eye movement: cerebral cortex detects and moves a new direction, so it can regain a visual input “I have to see something”.
35
Q

How does the spotting help with readjustment?

A

suppress the cerebral reaction; hope the vestibular-oculo gets used to quickly

36
Q

What is caused by spontanous nastagmus?

A

Imbalance of vestibular system (maybe damage)

37
Q

What is caloric testing?

A
  • Injecting ice water into the ear, cold water dense and sinks -> test the vestibular organs in each ear separately.
  • warm water in fluid rising -> convection current in another direction, feeling like moving, eye will drift (nastagmus)
  • for someone in a coma, test if brain stem is damaged.
  • In clinical setting, use body-temp water to clean!!!

Neuro Quiz 2_yl (8 decks)

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