Vestibular System 19

Question 0

Def. Postural equilibrium (2 types)

How is it controlled?

Answer 0

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

Question 1

Def. Postural orientation

Answer 1

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

Question 2

Sensory sources used in order to maintain balance?

Answer 2

Vision
Somatosensory
Vestibular

Question 3

The vestibular system is not….

Answer 3

A major component of “consciousness”

Question 4

When vestibular system fails, it can cause?

Answer 4

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

Question 5

What does the vestibular system tell us?

Answer 5

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

Question 6

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

Answer 6

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

Question 7

3 planes of linear acceleration?

Answer 7

Medial-lateral
Anterior-posterior
Inferior-superior

Question 8

3 types of angular accelerations

Answer 8

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

Question 9

Vestibular organ location

Answer 9

Very close to the auditory system (cochlea)

Question 10

Vestibular organ is made up of what two parts?

Where are they found?

Answer 10

Semicircular canals - found within the ampullae

Otolith organs - found on the macula

Question 11

Nerve that transmits vestibular signals?

Answer 11

8th cranial nerve (aka vestibulochoochlear nerve)

• contains all the vestibular afferents

Question 12

How does organ tell us about accelerations?

Answer 12

Tiny “hair” cells within each organ

Question 13

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

Answer 13

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

Question 14

How do hair cells respond?

Answer 14

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

Question 15

How causes the response of the hair cells?

Answer 15

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

Question 16

The hair cells are NOT completely shut. This means?

Answer 16

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

Question 17

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

Answer 17

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

Question 18

Line in the middle of the macula is called?

Answer 18

Striola

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

Question 19

Two types of macula?

What is the difference?

Answer 19

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

Question 20

Otolith organs are sensitive to?

Answer 20

Linear acceleration

Question 21

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

Answer 21

Overlying gelatinous layer

“Otolithic Membrane”

Question 22

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

Answer 22

Otoconia

Question 23

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

Answer 23

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

Question 24

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

Answer 24

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

Question 25

Each otolith organ (utricle or saccule) codes...

Answer 25

Linear accelerations | In 2 dimensional plane

Question 26

"Combined" utricle and saccule code

Answer 26

Linear accelerations | In all 3 dimensions

Question 27

Semicircular canals hair cells are oriented ....

Answer 27

In the same direction | - all depolarize or hyperpolarize

Question 28

Semicircular canals themselves are organized? | Parts of canal?

Answer 28

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

Question 29

Semicircular canals are sensitive to

Answer 29

Angular accelerations

Question 30

Hair cells found in semicircular canals are found in?

Answer 30

The capula within the ampulla | - splits the ampulla into two

Question 31

Semicircular canals are filled with what | This has what affect on hair cells?

Answer 31

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

Question 32

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

Answer 32

Horizontal left works with horizontal right | Anterior canal of one side works with posterior of other side

Question 33

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 ?

Answer 33

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

Question 34

Semicircular canals code for what acceleration? How many dimensions?

Answer 34

Angular acceleration | All 3 dimensions

Question 35

Roles of the semicircular canals?

Answer 35

Helps control the eye in head (Gaze) | Also balance, head on body information

Question 36

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

Answer 36

Accelerations | Velocity does not change firing rate

Question 37

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

Answer 37

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

Question 38

Where does the 8th cranial nerve travel to? | Where does it go after?

Answer 38

Vestibular nuclei and cerebellum | Then sent down brain stem to vestibulospinal and reticulospinal tracts causing muscle contraction

Question 39

Relation between vestibular and visual?

Answer 39

Directly connected | Work together to control "gaze"

Question 40

Def. Vestibulo-ocular reflex

Answer 40

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

Question 41

Vestibular-somatosensory integration

Answer 41

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

Question 42

Galvanic stimulation used to?

Answer 42

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

Question 43

GVS is?

Answer 43

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

Question 44

Short latency response

Answer 44

Response SL | reflexive, hard to modulate

Question 45

Medium latency response

Answer 45

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

Question 46

Postural sway

Answer 46

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

Question 47

Highest contribution of vestibular system when walking?

Answer 47

During heal contact *note vestibular system is used at different levels during gait

Question 48

Lowest contribution from vestibular system during gait?

Answer 48

Initial toe off

Question 49

Depression of the cerebellum causes? Significance?

Answer 49

Increased postural sway - shows there is a role of the cerebellum - explains ml response

Question 50

Vestibular contributions when standing walking running?

Answer 50

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

Question 51

Gurfinkel paper purpose, results?

Answer 51

- 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