B&b Week 3 Lecture 2

Front 1

What are the three things that the vestibular system detects?

Back 1

1. gravity
2. linear acceleration
3. angular motion

Front 2

What is the otis capsule?

Back 2

The bony/osseus labyrinth
(in the petrous portion of the temporal bone)

Front 3

What does the membranous labyrinth contain?

Back 3

1. 5 vestibular organs
2. auditory cochlea
3. endolymphatic sac

Front 4

What are the 5 vestibular organs?

Back 4

- 3 semicircular canals (anterior, posterior, horizontal)
- 2 otoliths (utricle, saccule)

Front 5

What is the function of the semicircular canals?

Back 5

Detect angular acceleration (head rotations)

Front 6

What is the function of the otolithic organs?

Back 6

Sense body orientation and linear motion

Front 7

In which plane is the utricle?

Back 7

Horizontal

Front 8

Which movements does the utricle sense?

Back 8

backwark-forward
right-left

Front 9

In which plane is the saccule?

Back 9

Saggital

Front 10

Which movements does the saccule sense?

Back 10

up-down

Front 11

Where is perilymph located?

Back 11

The space between bony and membranous labyrinths (outside)

Front 12

Where is endolymph located?

Back 12

In contiguous open lumen of semicircular canals, utricle and saccule (inside)

Front 13

Is the perilymph similar in composition to extra or intracellular fluid?

Back 13

Extracellular
(low K+, high Na+)

Front 14

What is the endolymph similar to?

Back 14

Intracellular fluid (high K+, low Na+)

Front 15

What are the sensory epithelia of the semicircular canals called?

Back 15

Cristae

Front 16

What is the sensory epithelia of the utricle/saccule called?

Back 16

Maculae

Front 17

What are the special cells that sense endolymph movement?

Back 17

Vestibular hair cells

Front 18

What are the two types of hair on hair cells?

Back 18

1. Kinocilium (1/cell)
2. Stereocilia (60-100/cell)

Front 19

What cranial nerve interacts with hair cell?

Back 19

VIII - Vestibulocochlear

Front 20

In what direction does the cilia bundle move in excitation?

Back 20

Towards the kinocilium (increased firing of vestibular afferents to CNS)

Front 21

What is otoconia?

Back 21

Otolitic masses (calcium carbonate crystals) sit on top of otolithic membrane

Front 22

Where is otoconia?

Back 22

In the maculae of the utricle/saccule

Front 23

How does otoconia work?

Back 23

It detects gravity or foward movement: it is heavier than endolymph, therefore bends the hairs one way or the other with gravity

Front 24

What plane is the utricle in?

Back 24

Horizontal

Front 25

What plane is the saccule in?

Back 25

Vertical

Front 26

What is different in maculae from cristae?

Back 26

The hair cells are not all in the same orientation in the maculae

Front 27

What is the location of the vestibular nuclear complex?

Back 27

Dorsal pons and medulla beneath the 4th ventricle

Front 28

What are the 4 vestibular nuclei?

Back 28

1. Lateral (Deiter's)
2. Medial
3. Superior
4. Inferior

Front 29

What is the role of the lateral vestibular nucleus (Deiter's)?

Back 29

Maintenance of posture

Front 30

What is the tract that the vestibular nucleus travels down through the spinal cord?

Back 30

Lateral vestibulospinal tract

Front 31

Where does the lateral vestibulospinal tract cross?

Back 31

It doesn't
(it is ipsilateral)

Front 32

What is the target of the lateral vestibulospinal tract?

Back 32

Anterior horn of cord
- alpha and gamma motor neurons
- innervate gravity opposing muscles of limbs

Front 33

What is the function of the medial vestibular nucleus?

Back 33

- Influences neck/axial muscles
- Stabilizes head in space

Front 34

What is the primary input for the medial vestibular nucleus?

Back 34

Semicircular canals

Front 35

What is the pathway from the medial vestibular nucleus?

Back 35

- Medial vestibulospinal tract
(medial longitudinal fasciculus)

Front 36

Does the medial vestibulospinal tract cross?

Back 36

It is bilateral with most fibers ipsilateral

Front 37

What is the function of the superior and medial vestibular nuclei?

Back 37

Reflexive eye movements to stabilize visual image on retina in response to head turn (vestibulo-ocular reflex)

Front 38

What is the input for the superior/medial vestibular nuclei?

Back 38

Horizontal semicircular canal

Front 39

What muscles does the horizontal VOR control?

Back 39

left & right lateral recti
left & right medial recti

Front 40

What is the function of the inferior vestibular nucleus?

Back 40

Integration of vestibular, multi-sensory and cerebellar inputs to calibrate reflex responses

Front 41

What is it called when there is "rhythmic alteration of slow and fast eye movements during VOR"?

Back 41

nystagmus

Front 42

T/F: temperature induces convective flow of endolymph within the horizontal semicircular canal

Back 42

T

Front 43

What does the temperature difference simulate?

Back 43

Head rotation

Front 44

Which way will the eyes rotate if you put cold water in the left ear?

Back 44

Right
(COWS: cold-opposite, warm-same)

Front 45

What are some symptoms of bilateral vestibular dysfunction?

Back 45

- slow onset of loss
- oscillopsia (oscillating instability of eyes with head movements)
- instability when walking in dark

Front 46

What are some symptoms of unilateral vestibular dysfunction?

Back 46

- extreme dizziness
- nausea, vomitting
- deviation towards side of lesion when walking
- nystagmus

Front 47

What is dizziness induced by?

Back 47

Mismatch between vestibular and visual inputs

Front 48

What is rotation-induced dizziness?

Back 48

Prolonged head rotations - cupula restores head to upright - doesn't match visual input

Front 49

What is false visual motion?

Back 49

Visual input (car moving forward beside you) doesn't match vestibular input (you aren't moving)

Front 50

What is motion sickness?

Back 50

Vestibular activation without coordinated visual input
(inside boat - not seeing swells)

Front 51

What does alcohol do to the vestibular system?

Back 51

Changes density of endolymph giving false vestibular input