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Neuromuscular Physiology > Vestibular System 19 > Flashcards

Vestibular System 19 Flashcards

0
Q

Def. Postural equilibrium (2 types)

How is it controlled?

A

Postural equilibrium = balance
Static: body is at rest (motionless)
Dynamic: applied and internal forces acting on body are balanced (no acceleration)
– control COM within COP

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1
Q

Def. Postural orientation

A

Relative positioning of the body segments with respect to “each other” and “the environment”

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2
Q

Sensory sources used in order to maintain balance?

A

Vision
Somatosensory
Vestibular

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3
Q

The vestibular system is not….

A

A major component of “consciousness”

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4
Q

When vestibular system fails, it can cause?

A

Also when receives a lot of input
Contradictory signals can make u very sick

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5
Q

What does the vestibular system tell us?

A

Head accelerations
Angular accel. - nodding
Linear accel. - gravity

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6
Q

Physical features that make up the vestibular system (aka labyrinth)

A

Peripheral apparati imbedded bilaterally in the head (one per ear)

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7
Q

3 planes of linear acceleration?

A

Medial-lateral
Anterior-posterior
Inferior-superior

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8
Q

3 types of angular accelerations

A

Pitch (yes)
Roll (maybe)
Yaw (no)

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9
Q

Vestibular organ location

A

Very close to the auditory system (cochlea)

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10
Q

Vestibular organ is made up of what two parts?

Where are they found?

A

Semicircular canals - found within the ampullae

Otolith organs - found on the macula

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11
Q

Nerve that transmits vestibular signals?

A

8th cranial nerve (aka vestibulochoochlear nerve)

  • contains all the vestibular afferents
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12
Q

How does organ tell us about accelerations?

A

Tiny “hair” cells within each organ

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13
Q

Vestibular organ has two types of cilia (hair cells)
How many of each?
What’s their formation?

A

Kinocilium (1 per cell)
Stereocilia (40-70)
- increase in length from one end of cell to the
- cilia are attached to one another

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14
Q

How do hair cells respond?

A

Bending of the stereocilia towards the kinocilium cause “depolarization”
(Away from causes hyperpolarization)

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15
Q

How causes the response of the hair cells?

A

Gated channels open and close depending on direction of bending

  • potassium enters cell causing depolarization
  • depol opens voltage gated Ca channels
  • Calcium increase potential towards -55, to generate AP
  • Ca causes release of neurotransmitter
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16
Q

The hair cells are NOT completely shut. This means?

A
  • there is a constant influx of potassium
  • 8th cranial nerve is always firing
    (Tonic firing rate of ~100Hz)
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17
Q

Orientation of hair cells is extremely important. What’s difference between semicircular canals and otolith organs?

A 
Semicircular
- hair cells found within the ampullae
- all cells face 1 directions
Otolith 
- found within maculae 
- multiple directions
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18
Q

Line in the middle of the macula is called?

A

Striola

  • otolith organs hair cells face multiple directions
  • kinocilia of hair cells either point towards or away from striola
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19
Q

Two types of macula?

What is the difference?

A

Utricle - horizontal acceleration - kinocilia face towards striola
Saccule - vertical accel. - kinocilia face away from striola

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20
Q

Otolith organs are sensitive to?

A

Linear acceleration

21
Q

Hair cells of the otolith organs (macula) project into the …

A

Overlying gelatinous layer

“Otolithic Membrane”

22
Q

Name of the small crystals imbedded in the otolithic membrane of the macula?

A

Otoconia

23
Q

What recognizes linear accelerations of the head? (Head tilts)

A 
Otolith organs (macula)
- causes shearing of the otolithic membrane
24
Q

How to tell the difference between acceleration (sitting in a car) and head tilt?

A

Use other sensory sources (receptors in the neck sense tilt)

25
Q

Each otolith organ (utricle or saccule) codes…

A

Linear accelerations

In 2 dimensional plane

26
Q

“Combined” utricle and saccule code

A

Linear accelerations

In all 3 dimensions

27
Q

Semicircular canals hair cells are oriented ….

A

In the same direction

- all depolarize or hyperpolarize

28
Q

Semicircular canals themselves are organized?

Parts of canal?

A

3 semicircular canals arranged ORTHOGONALLY (90 degrees to each other) - to pick up accel in each direction

  • horizontal, posterior and superior canals organized as one SCC
29
Q

Semicircular canals are sensitive to

A

Angular accelerations

30
Q

Hair cells found in semicircular canals are found in?

A

The capula within the ampulla

- splits the ampulla into two

31
Q

Semicircular canals are filled with what

This has what affect on hair cells?

A

Endolymph fluid

Rotation causes fluid to lag behind (inertia) - bends cilia opposite direction of the angular acceleration

32
Q

Membranous ducts of semicircular canals work in pairs. What works with what?

A

Horizontal left works with horizontal right

Anterior canal of one side works with posterior of other side

33
Q

Because semicircular canals are set up as mirror image, and kinocilia face same direction, head turn will cause the pair of canals to have what output response ?

A

Opposite
Depol (increase firing) in one side
Hyperpol (decrease firing) other side

34
Q

Semicircular canals code for what acceleration? How many dimensions?

A

Angular acceleration

All 3 dimensions

35
Q

Roles of the semicircular canals?

A

Helps control the eye in head (Gaze)

Also balance, head on body information

36
Q

Only what type of movement changes firing rate of vestibular afferents?

A

Accelerations

Velocity does not change firing rate

37
Q

Damage to the vestibular system, symptom may be irregular movements of the eyes called? What’s its definition? Experimentally induced? What is this reflex?

A

Nystagmus
Slow smooth movement of eyes in one direction followed by fast in the other direction
Experimentally induced by spinning in circle fast
Vestibulo-ocular reflex

38
Q

Where does the 8th cranial nerve travel to?

Where does it go after?

A

Vestibular nuclei and cerebellum

Then sent down brain stem to vestibulospinal and reticulospinal tracts causing muscle contraction

39
Q

Relation between vestibular and visual?

A

Directly connected

Work together to control “gaze”

40
Q

Def. Vestibulo-ocular reflex

A

Accelerations picked up by SCC, activate pathways to rotate eyes
-works in darkness, does not require vision

41
Q

Vestibular-somatosensory integration

A

Vestibular and neck spindles + skin feedback provide head on body Proprioception

42
Q

Galvanic stimulation used to?

A

Determine pathways
How body uses information
How body integrates info with other sensory sources

43
Q

GVS is?

A

Non invasive technique to test function of vestibular system

  • pass electric current behind ear to stim 8th cranial nerve
  • increases FR on cathode afferents and decrease anode side
44
Q

Short latency response

A

Response SL

reflexive, hard to modulate

45
Q

Medium latency response

A

Response ML

Occurs later in time, opposite response to SL, correlated to balance, easy to modulate

46
Q

Postural sway

A

Movement of the COP to maintain whole body stability

- sensed by vestibular info about the head and somatosensory about spindles and skin of the neck

47
Q

Highest contribution of vestibular system when walking?

A

During heal contact

*note vestibular system is used at different levels during gait

48
Q

Lowest contribution from vestibular system during gait?

A

Initial toe off

49
Q

Depression of the cerebellum causes? Significance?

A

Increased postural sway

  • shows there is a role of the cerebellum
  • explains ml response
50
Q

Vestibular contributions when standing walking running?

A

Standing - Not much movement (use more visual somatosensory)
Walking - very important, particularly heal contact
Running - not as important - pre planned motor program

51
Q

Gurfinkel paper purpose, results?

A
  • determine if vestibulomotor response will adapt to changed perception of head position during prolonged status head turn
  • direction of sway changed with perception of head location, over time thought returned to normal so returned to medial lateral sway
  • perception of head wrt body, not actual position

Neuromuscular Physiology (8 decks)

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