Vestibular system Flashcards
(46 cards)
1
Q
Sensory purpose of
vestibular system
A
- perception of motion and orientation
- angular acceleration
- linear acceleration: up and down or left and right
- position in relation to gravity
2
Q
motor purpose of
vestibular system
A
- control of eye movement to permit clear visual image of surrounds
- maintenance of equilibrium and desired posture
3
Q
Vestibular structures: periphery
A
- ear
- vestibular apparatus: vestibular receptors and cranial nerve axons
4
Q
vestibular strucutres: CNS
A
- Vestibular nuclei in brainstem
- cerebral cortex (vestibular cortex)
5
Q
Describe how information travels
A
- sensory information from ear converted into neural signals
- vestibular nerve => vestibular nuclei (w/i) brainstem)
6
Q
Vestibular nuceli projections provide
A
- sensory input about head movement and position
- gaze stabilization
- postural adjustments autonmic function and consciousness
7
Q
how do the canals detect movement of the head
A
- detect angular acceleration of the head (change while it’s happening)
- beginning of rotation; endolymph stays behind
- rotation maintained; endolymph catches up
- rotation stops; endolymph keeps going
8
Q
hair cell firing
A
- head stationary = baseline rate
- head begins to turn: inertia causes fluid in canal to lag behind; deflects cupula, bends cilia
- hair bending: changes baseline rate hair cells firing - determining frequency of signals sent to the vestibular nerve
9
Q
Describe cupula deflection
A
- head movement in one direction
- fluid in canal moves the other
10
Q
what are the functional pairs of the canals
A
- both horizontal
- right anterior loop and left posterior loop
- left anterior loop and right posterior loop
11
Q
What do the functional pairs do
A
- maxium fluid flow in each SCC: occurs during movement in a single plane
- max flow in pairs prevents stimulation of other canals
- reciprocal signals: one increases and one decreases
12
Q
Non-reciprocal signals
A
if signals from pain are not reciprocal
- postural control abnormalities
- abnormal eye movement = nystagmus
- nausea
13
Q
Otolith organs
A
- utricle and saccule comprise medial portion of the vestibule
- each organ contains sensory hair cells embeded within a membrane with otoconia attached to the medial wall of saccule and floor of utricle
- specific gravity of otoconia is greater than the surrounding endolymph
- responsive to linear acceleration forces, example: gravity
14
Q
Macula
A
- receptor inside the utricle and saccule
- hairs projecting are embedded in a gelatinous material.
- Atop the gelatinous material are otoliths, which are small, heavy, sandlike crystals.
- When the macula is moved into different positions, the weight of the otoliths bends the hairs, stimulating the hair cells and changing the pattern of vestibular neuron firing.
15
Q
How do the otolith crystal change with age
A
- Increased variability in size
- Hypertrophy
- Fragmentation
- Fissured
- Pitted
- Weakening of linkages
16
Q
vestibular system
Vascular supply
A
- Originates from the basilar artery (posterior circulation)
Primary supply for the vestibule is as follows:
- Basilar → AICA → Labyrinthine artery → Anterior vestibular artery—supplies anterior and horizontal semicircular canals and the utricle
- Basilar → AICA → Labyrinthine → common cochlear → posterior vestibular artery - supplies posterior canal and saccule
17
Q
Neural innervation
A
- superior portion of VII nerve innervates anterior and horizontal canals and utricle
- Inferior portion of VIIIth nerve innervates posterior canal and saccule
18
Q
what is the vestibular nerve made of
A
- Vestibular nerve made up of bipolar neurons of vestibular ganglion
- Distal axon
- Vestibular nerve
- Proximal axon
- CN VIII
19
Q
whats included in the central vestibular system
A
- four vestibular nuclei
- six pathways
- vestibulocerebellum
- vestibular cortex
20
Q
What are the vestibular nuclei
A
- Superior
- lateral
- medial
- inferior
- most output via cranial nerve VIII to vestibular nuclei in the medulla
- some fibers project directly to cerebellum
21
Q
Vestibulocerebellum
A
- projects to cerebellum
- inputs from vestibular apparatus
- to eye influence eye movements, vestibular nuclei, balance and equilibrium
22
Q
What are the 6 pathways in the central vestibular system
A
- pathways that convey information from vestibular nuclei
- medial longitudinal fasciculus
- vestibulospinal tracts
- vestibulocollic
- vestibulothalamocortical
- vestibulocerebellar
- vestibuloreticular
23
Q
Medial longitudinal fasciculus (MLF)
A
- helps VOR
- to extraocular nuclei and superior colliculus
- influences eye and head movements
24
Q
Vestibulospinal tracts
A
- to LMNs
- influence posture
25
Vestibulocollic
- to nucleus of accessory nerve
- influences head position
26
Vestibulothalamocortical
- conscious awareness of head position and movement
27
Vestibulocerebellar
- to vestibulocerebellum
- controls magnitude of muscle responses to vestibular info
- including VOR
28
vestibuloreticular
| pathway
- to reticular formation
- autonmoic centers for nausea/vomiting
- center of brainstem
29
# Vestibular system function
motor control
- gaze stabilization: VOR
- postural adjustments
30
# motor control
postural adjustments for vestibular system
| how does it work
`reciprocal connections between vestibular nuclei and `
- spinal cord
- reticular formation
- superior colliculus
- CN XI nucleus
- cerebellum
## Footnote
even when someone is a coma the eye will follow if they dont = brain dead
31
Vestibulocortex
- parietal insula
- lesion = change in awareness of head position and head movement and perception of vertical
32
Vestibular reflexes
| the types
- VOR: vestibulo-ocular reflex
- VSR: vestibulospinal reflexes *stabilizes head and body*
33
VOR
| what does it do
- produces eye movements of same velocity as head movement
- opposite direction
34
Vestibulospinal reflexes for postural adjustments
- reciprocal connections between vestibular nuclei and
- spinal cord
- reticular formation
- superior colliculus
- cerebellum
35
descending tracts with vestibular system
- lateral vestibulospinal tracts: activates postural muscles in limbs and trunk
- medial vestibulospinal tracts: coordinates head and eye movements
36
# Vestibular disease
effects
decreased balance and gaze stability
37
# vestibular disease
signs and symptoms
- vertigo: spinning/cannot focus eyes/feeling of movement
- disequilibrium: feel off balance
- blurred vision with head movement (nystagmus)
38
dizziness
- a whirling sensation in the head
- giddy
- mentally confused
- off balance
39
Vertigo
false sense of rotation
40
oscillopsia
- gaze instability
41
imbalance
unsteadiness (observable)
42
disequilibrium
- subjective sense of imbalance
43
lightheadedness/presyncope
feeling of faintness
44
Nystagmus
- involuntary eye movement
- abnormal VOR
- slow movements in one direction VOR
- faster movement in opposite direction (saccade)
45
types of eye movement with nystagmus
- abduction/adduction
- elevation/depression
- torsion
46
Vestibular nystagmus
| based on what is involved
- w/ crystals = nystagmus toward involved side
- w/ vestibular nerve = nystagmus away from involved
## Footnote
goes toward active side
