Vestibular System Flashcards
Vestibular information is essential for what 2 things?
- postural control
- control of eye movements
Vestibular information is converted into neural signals that are conveyed by the _____ nerve to the _____ nuclei located in the brainstem at the junction of _____ and _____.
vestibular
vestibular
pons and medulla
What happens to the vestibular information that reaches the parietal cortex?
A 3-D space is constructed from it for a sense of dizziness by abnormal vestibular stimuli
What are the 4 things projections from the vestibular nuclei contribute to?
- Sensory information about head movement and head position relative to gravity
- Gaze stabilization (i.e., control of eye movements when the head moves)
- Postural adjustments
- Autonomic function and consciousness
What anatomical structure houses all vestibular organs?
The vestibular apparatus
What does the vestibular apparatus consist of?
A bony and membranous labyrinths and hair cells
The bony labyrinth is a convoluted space within the skull that contains _ semicircular canals and _ otolithic organs
3
2
Where is the membranous labyrinth found and what does it consist of?
It is within the bony labyrinth and consists of a hollow canal filled with endolymph which contains hair cells
How does receptors in the semicircular canals detect movement?
By sensing the motion of the endolymph
Each semicircular canal opens at both ends into what?
one of the otolithic organs
The swelling located at the end of each semicircular canal is called what? What is located within this structure?
An ampulla, which contains a crista. This crista consists of supporting cells and sensory hair cells
What are the sensory hair cells embedded in?
A gelatinous mass called the cupula
The receptors in the semicircular canals are only sensitive to what type of movements?
rotational acceleration or deceleration (i.e., speeding up or slowing down rotation of the head)
When does maximal fluid flow/change in frequency occur?
When the head turns on the canal’s axis of the rotation
What are the 3 semicircular canals?
- anterior
- posterior
- horizontal
What are the 3 pairs in which fluid moves in the semicircular canals?
(1) Left with right horizontal canals
(2) Left anterior with right posterior
(3) Left posterior with the right anterior
Each canal in a pair produces ____ signals, so that increased signals from one canal occur simultaneously with ______ signals from its partner
reciprocal
decreased
These reciprocal signals are essential for what?
normal vestibular function
If the signals from a pair of semicircular canals is not reciprocal what is the result?
- abnormal control of posture
- abnormal eye movements
- nausea
What are the names of the 2 otolithic organs?
utricle and saccule
What are the otolith organs sensitive to?
head position relative to gravity and to linear acceleration and deceleration
In each of the otolith sacs is a ____, consisting of hair cells enclosed by a gelatinous mass topped by calcium carbonate crystals
macula
What are the calcium carbonate crystals located within the macula called?
Otoconia
Describe what happens within the otolith organs when the head is tilted.
The weight of the otoconia displace the gelatinous mass, bending the embedded hair cells either stimulating or inhibiting them
What is most of the information derived from the semicircular canals used for?
to stabilize vision, i.e., the information keeps eyes on a target when the head turns
What is most of the information derived from the otolithic organs used for?
to adjust activity in the lower motor neurons to postural muscles
What does the peripheral part of the vestibular system consist of?
The vestibular apparatus and the peripheral part of the vestibular nerve
One vestibular information is transmitted to the vestibular nuclei in the pons and medulla what happens next?
It is transmitted to the floculonodular lobe in the cerebellum
What is the major function of the vestibular nuclei?
To coordinate movements of the eyes and head to allow for stable visual fixation during head movement
What does the central part of the vestibular system consist of?
- 4 nuclei
- 6 pathways
- the vestibulocerebellum
- the vestibular cortex
Where are the 4 nuclei located?
Bilaterally at the junction of the pons and medulla, near the fourth ventricle
What are the 4 vestibular nuclei called?
lateral, medial, inferior, and superior vestibular nuclei
The medial longitudinal fasciculus connects the vestibular nuclei with what 3 things?
- nuclei that control eye movements
- the superior colliculus
- the nucleus of cranial nerve XI (accessory nerve)
Where do the medial and lateral vestibulospinal tracts convey vestibular information to?
To the spinal cord, to adjust activity in postural muscles
Describe the flow of information following angular acceleration of the head
1) semicircular canals
2) vestibular nuclei and vestibuloerebellum
3) vestibular cortex (head orientation), oculomotor nuclei (eye movements), and spinal cord (postural control)
Describe the flow of information following linear acceleration of the head
1) saccule and utricle
2) vestibular nuclei and vestibuloerebellum
3) vestibular cortex (head orientation), oculomotor nuclei (eye movements), and spinal cord (postural control)1) semicircular canals
2) vestibular nuclei and vestibuloerebellum
3) vestibular cortex (head orientation), oculomotor nuclei (eye movements), and spinal cord (postural control)
What are the 6 pathways that convey information from the vestibular nuclei?
- medial longitudinal fasciculus
- vestibulospinal tracts
- vestibulocolic pathways
- vestibulothalamocortical pathways
- vestibulocerebellar pathways
- vestibuloreticular pathways
What are the 2 roles the vestibular system has in motor control?
- Gaze stabilization
- Postural adjustments
What is gaze stabilization operated by?
the vestibulo-ocular reflex
How are postural adjustments achieved?
Via reciprocal connections between the vestibular nuclei and the spinal cord, reticular formation, superior colliculus, nucleus of cranial nerve XI, and cerebellum
