Neuro Vestibular System Burrell Ssom

Front 1

Vestibular System
(overview)

Back 1

mediates our sense of balance and orientation
critical in maintaining visual fixation in response to head rotation
we are unconscious of function unless not working

Deficits:
profound effects on vision and sense of balance
can indicate damage at brain stem

Front 2

Vestibular apparatus
(components, location)

Back 2

series of interconnected canals (labyrinth) encased in temporal bone along with cochlea

3 semicircular canals
2 sack-like structures: sacculus & utricle (otolith organs)

Front 3

Semicircular canals
(function)

Back 3

detect rotational movements of head
(rotational or angular acceleration)

Front 4

Sacculus and Utricle
(functions)

Back 4

(1) detect linear acceleration
(2) detect static position of head

Front 5

Vestibular hair cells
(role, similar to, components)

Back 5

actual sensory neuron of vestibular system
similar to cochlear hair cells
single kinocilium
tuft of stereocilia

Front 6

Kinocilium and stereocilia
(stereocilia have _ channels,
gated by _)

Back 6

with K+ channels at tip gated by stereocilium movement relative to kinocilium

Front 7

Stereocilia
The channels _ when stereocilia move toward the kinocilium, _ the hair cell and _ transmitter release

Back 7

open
depolarizing
increasing

Front 8

Stereocilia
The channels _ when stereocilia move away from the kinocilium, _ the hair cell and _ transmitter release

Back 8

close
hyperpolarizing
decreasing

Front 9

What do the hair cells do when not being moved?

Back 9

release NT all the time
thus constant level of activity (action potentials) in vestibular nerve that increases or decreases based on movements of stereocilia

Front 10

Because hair cells have _ their orientation is important

Back 10

directionality

Front 11

Where do the hair cell all have the same orientation?

Back 11

ampulla (part of semicircular canals)
they all respond in the same way to motion in the preferred direction

Front 12

How are the hair cells oriented in the sacculus and utricle?

Back 12

hair cells on one side are all oriented in one direction
those on other side all oriented in opposite direction
striola forms the divide that separates the two populations of hair cells

Front 13

_ forms the divide that separates the two populations of hair cells in sacculus or utricle?

Back 13

Striola

Front 14

For sacculus and utricle, where are the hair cells located?

Back 14

macula

Front 15

Kinocilium and stereocilia are surrounded by gelatinous matrix and on top of this gelatinous layer is the _
Embedded within it are crystals of calcium carbonate called _

Back 15

otolithic membrane
otoconia (otoliths) = ear stones

Front 16

When head tilts the _ move relative to the hair cells and this movement does what?

Back 16

otoconia/otolithic membrane
bends the hair bundles

Front 17

_ also produces movement by the otolithic membrane relative to the hair cells b/c the greater relative mass of the otolithic membrane and the fact it "floats" on a gelatinous layer.
Thus the otolithic membrane _ every time the head/body _

Back 17

linear acceleration/deceleration

lags
acc/decel

Front 18

Macula of utricle is oriented in _ plane and therefore detects _ and _

Back 18

horizontal
sideways tilting of head and
lateral movements

Front 19

Macula of sacculus is oriented in _ plane and detects _ and _

Back 19

vertical
forward/backward head tilts and
movements along sagittal plane

Front 20

As a result of opposing orientations of hair cells, a given amount of movement in a given direction will _ some hair cells and _ others
resulting pattern of activity can thus _

Back 20

excite
inhib

encode any combo of head movements/positions

Front 21

In sacculus, hair cells oriented _ the striola

Back 21

away from

Front 22

In the Utricle, the hair cells are oriented _ the striola

Back 22

toward

Front 23

Vestibular Apparatus
(label)

Back 23

Front 24

Kinocilium and Stereocilia
On top, label hyperpol and depol
On bottom, label increase or decrease in firing

Back 24

Front 25

Label

Back 25

Organization of Macula including
hair cells, otolithic membrane, otoconia
(note: different orientation on either side of striola)

Front 26

Each of the three semicircular canals has swelling at base called _
the hair bundles are surrounded by gelatinous mass called the _

Back 26

ampulla

cupula

Front 27

Semicircular canals and ampulla
(location of hair cells)

Back 27

within ampulla

Front 28

ampulla

Back 28

swelling at base of semicir canals

Front 29

The hair bundles are surrounded by a gelatinous mass called _

Back 29

cupula

Front 30

Semicircular canals filled with _

Back 30

endolymph

Front 31

When the head rotates, the inertia of the endolymph produces a force or wave that transmits thru the semicircular canal in _ direction
This causes _ to be displaced, bending the _
Hair cells in ampulla are all oriented in same direction, therefore movement _

Back 31

opposite
(coffee in cup when car stops)

cupula
hair cell tufts

either stimulates or inhibs all the hair cells

Front 32

Label

Back 32

Arrangement of ampulla and cupula in semicircular canals
Note: hair cells all have same orientation

Front 33

What is the orientation of the semicircular canals in the head?

Back 33

Front 34

Each of semicircular canals is oriented to detect _
Also, the canals work in _

Back 34

rotation in single plane

complimentary pair
(ex. horizontal canal of left and right)

Front 35

If head turns left,
hair cells in _ canal excited and
_ canal inhibited

Back 35

left excited
right inhibed
*side excited corresponds to direction of rotation

(brain used this info from complimentary pairs of canals to determine direction of rotation)

Front 36

Label and
What is the diagram showing?

Back 36

How a complementary pair of semicircular canals detect rotational movements

Front 37

Each hair cell in vestibular apparatus synapses onto _ whose soma are located in _
The processes then project to CNS via _ of _
Primary target is _ nucleus, but also direct projections to _

Back 37

bipolar cells
vestibular ganglion (Scarpa's ganglion)
vestibular division of
vestibulocochlear nerve (CNVIII)
vestibular nucleus
cerebellum

Front 38

Vestibular nucleus
(location, divisions)

Back 38

medulla
superior, inferior, lateral, medial

Front 39

Central vestibular pathways
(1)
vestibular nuclei project to motor nuclei that innervate _
bilateral pathway via _
functional role is _

Back 39

extraocular muscles
ascending projection in MLF
mediate VOR

Front 40

Central vestibular pathways
(2)
Two separate connections to _
One is via _
bilateral projections that terminate at _ level and mediate _ and _

Second is _
this pathway projects to ipsilateral motor nuclei in _ that innervate _
functional role is to _

Back 40

spinal cord

descending MLF
cervical level of SC
postural control of head and neck and
coordinate head movements with VOR

vestibulospinal tract (lateral vestibulospinal tract)
ipsi motor nuclei in ventral horn that innervate trunk and limb muscles
maintain posture and balance (excite leg extensors, inhib leg flexors)

Front 41

Central vestibular pathways
(3)
projection to _
specifically _
Includes two main pathways
One is direct connection from _ to _
The other involves projections from vestibular nuclei to cerebellum thru _
The _ has its own input onto vestibular nuclei and these play impo role in _

Back 41

cerebellum
vestibulocerebellum
(flocculonodular lobe, adj vermis, fastigial nucleus)

vestibular ganglion to cerebellum

juxtarestiform body

vestibulocerebellum
maintenance of balance and modulation of ocular reflexes

Front 42

Central vestibular pathways
(4)
vestibular nuclei have ascending projections to _ which then project to _

Back 42

posterolateral thalamus
many different cortical regions
(no single "vestibular cortex",
two prominent regions are temporal-insular and parietal-insular,
other regions are hippocampal formation, amygdala, anterior cingulate gyrus)

Front 43

Adaptation of vestibular system

Back 43

very good at adapting to persistent and sometimes inappropriate input
many vestibular dysfunctions that affect balanced treated with positional therapy which takes advantage of adaptation
the ability of vestibular system to adapt it due to modulatory input from cerebellum

Front 44

Vertigo vs. Dizziness

Back 44

vertigo = sense that one is spinning or that enviro is spinning

dizziness = less exact term, could describe feeling of loss of balance, light headed, nausea

Front 45

Vertigo
(due to lesions _ or _, impo to distinguish?)

Back 45

peripheral level:
(vestibular app or vestibular nerve)

central level:
(brainstem or cerebellum)

impo to distinguish b/c central are indicative of potentially fatal strokes

Front 46

How distinguish b/w peripheral or central causes of vertigo?

Back 46

positional testing:
with head to left or right, patient quickly transitioned from sitting to lying postion to cause max stimulation of posterior semicir canals in ear that is down and elicits nystagmus and vertigo in either peripheral or central disorders
onset, adaptation, type of nystagmus, etc. will tell distinguish central vs. peripheral

Front 47

Vertigo due to peripheral disorders
After position testing _

Back 47

onset of nystagmus and vertigo delayed (2-5 s)
nystagmus horiz or rotary and does NOT change direction
nystagmus and vertigo only seen together
nystag and vert adapt if test repeated within 30sec

Front 48

Vertigo due to central disorders
After position testing _

Back 48

onset of nystag and vert can be immediate
nystag may be horiz, rotary, or vert and CAN change direction
nystag may be seen without vert
no adaptation observed

Front 49

Peripheral Vestibular Disorders
(name)

Back 49

Most cases of vertigo due to peripheral:
benign paroxysmal positional vertigo (BPP)
vestibular neuritis
Meniere's disease

Front 50

benign paroxysmal positional vertigo (BPP)

Back 50

most common peripheral vertigo
brief period of vertigo that occurs with change in position (sitting to standing, etc.)
first occurence severe (as long as hours)
subsequent short (few seconds)
cause probably debris within semicircular canal that pushes cupula
only treatment adaptation exercises,
although condition often resolves over time

Front 51

vestibular neuritis

Back 51

swelling of vestibular nerve or ganglion
possibly due to infection
can lead to intense vertigo that lasts for several days
second-most likely peripheral vertigo
Tx: steroidal anti-inflam drugs

Front 52

Meniere's disease

Back 52

recurring episodes of vertigo and
progressive loss of hearing
(tinnitus is another frequent symptom)
exact cause unknown but thought excessive pressure generated in endolymph of semicircular canals leading to increased activity of vestibular system
Tx:
salt restriction or diuretics
(there are also surgical procedures)

Front 53

Central Vestibular disorders
(name)

Back 53

Wallenberg's syndrome
Downbeat Nystagmus (DBN)

Front 54

Wallenberg's syndrome

Back 54

most common central vestibular disorder
lesion of lateral medulla

Vestibular symptoms:
vertigo and nystagmus

Other symptoms:
ataxia, decrease PT ipsi face, decrease PT contra body, Horner syndrome, difficulty swallowing

vertigo and nystagmus also observed in lesions of lateral pons (lateral pontine syndrome)

Front 55

Central Vestibular disorders
(lesions of _)

Back 55

lesions of vestibular nuclei or MLF can cause vestibular dysfunctions that include vertigo and nystagmus
likely to accompany other motor or somatosen deficits

Front 56

Downbeat Nystagmus (DBN)

Back 56

lesions of vestibulocerebellum produce ataxia and DBN
DBN is a fixational nystagmus in which movement of eye is straight down
(can be induced by having patient fix their gaze on an object)

Front 57

Vertigo
(other causes)

Back 57

alcohol
some anticonvulsants
some antibiotics
even aspirin

Front 58

Caloric test

Back 58

test of vestibular system function in coma patients to assess brainstem function
patient on back with head elevated 30 degrees
cold or warm water irrigated into one ear
temp change induced by water generates convection current in endolymph of semicircular canal that causes movement of the endolymph that mimics head rotation
this elicits VOR
VOR has slow eye move in oppo followed by fast eye move in same direction
In patients with intact brainstem, *rapid* eye movement predicted with:
Cold water
Opposite
Warm Water
Same
(COWS)

Front 59

Label and
For Pathways Name Function

Back 59