Glossary of Vestibular System 2
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- What are the 3 sources other than the cutaneous exteroceptors that the body uses to determine its position in space?
- What are the 2 subdivisions of the vestibular system?
- Static labyrinth
- What is the function of the static labyrinth?
- detection of linear acceleration and gravity
- What are the 2 parts of the static labyrinth?
- Saccule and utricle, both with macula
- What is located in the macula?
- Hair cells and otolithic membrane
- Describe the hair cells of the macula
- Cells with stereocilia whose "hairs" are embedded in the otolithic membrane and have a single rigid kinocilium
- Describe the otolithic membrane of the macula
- A gelatinous substance with embedded calcium carbonate particles. The "hairs" are embedded in it.
- What does the saccule connect with?
- The cochlear duct
- How is the macula oriented in the saccule?
- How is the macula oriented in the utricle?
- What is the function of the utricle?
- Monitors acceleration and tilting of the head
- What are 2 actions that can displace the otolithic membrane?
- Linear acceleration of the head
Change in head position
- What happens when the otolithic membrane is displaced?
- Stereocilia that are embedded in the membrane bend, either towards or away from the kinocilium
- What happens when the hair cells are bent towards the kinocilium?
- What happens when the hair cells are bent away from the kinocilium?
- What is the function of the kinetic labyrinth?
- Detection of angular acceleration
- How many semicircular canals are in the kinetic labyrinth?
- What is the arrangement of the semicircular canals?
- perpendicular to each other
- What is the relationship of the anterior canal with the posterior canal of the opposite side?
- in line with it
- What is the relationship of the posterior canal with the anterior canal of the opposite side?
- in line with it
- What is the relationship of the lateral canal with the other canals?
- Horizontally, off by 30 degrees
- Where is the sensory portion of these canals?
- In a dilated portion called the ampulla
- What are the special receptor sites in the ampullae called?
- What is located in the cristae of the ampullae?
- Hair cells
- Where are the stereocilia of the hair cells embedded?
- Flow of ---- caused by ----- acceleration of head causes displacement of ------ which results in stimulation of -----
- endolymph, angular, cupula, hair cells
- What are vestibular (Scarpa's) ganglion cells?
- biploar cells
- Where do the peripheral processes of vestibular ganglion cells synapse?
- hair cells of the vestibular apparatus
- What do the central processe of vestibular ganglion cells make up?
- vestibular portion of the vestibulocochlear nerve
- What are the 3 vestibular nuclei in the brainstem?
- Lateral vestibular nucleus (Dieter's)
Medial vestibular nucleus
Superior vestibular nucleus
- What does the lateral vestibular nucleus (Dieter's) form? Why is this important?
- Vestibulospinal tract, important in posture
- What does the medial vestibular nucleus form? Why is this important?
- Contributes to the medial longitudinal fasiculus, important in vestibulo-occular reflexes
- Where do the superior and inferior vestibular nuclei project to? What is their function?
- Cerebellum, integration and modulation of posture
- Some vestibular fibers terminate directly in the ---- as ---- fibers
- archicerebellum, mossy
- Where do vestibular afferents terminate?
- Vestibular nuclei
- What are the 2 pathways that the vestibular nuclei have connections from the cerebellum?
- Direct Purkinje cell axons
Fibers from fastigial nucleus
- What is the action of direct Purkinje cells from the cerebellum to the vestibular nuclei?
- What is the action of fibers from the fastigial nucleus from the cerebellum to the vestibular nuclei?
- Where does the vestibulospinal tract originate?
- lateral vestibular nucleus
- Does the vestibulospinal tract run ipsi or contralaterally?
- Where in the spinal cord does the vestibulospinal tract run?
- all levels
- where do the vestibulospinal tract fibers synapse?
- Verntral horn cells
- What is the action of vestibulospinal tract fibers?
- excite extensors
- Why is the vestibulospinal tract important?
- postural adjustments to vestibular stimulation
- What are the 2 subdivisions of the median longitudinal fasiculus?
- descending and ascending limb
- Where does the descending limb of the MLF originate?
- all vestibular nuclei, but particularly the medial
- Where in the spinal cord does the descending limb of the MLF run to?
- bilaterally to cervical spinal cord
- Where do the fibers of the descending limb of the MLF synapse?
- Ventral horn cells
- What is the function of the descending limb of the MLF?
- Reflex turning of the head to vestibular stimulation
- Where do the fibers of the ascending limb of the MLF have inputs to?
- abducens, trochlear, and occulomotor nuclei
- What is the function of the ascending limb of the MLF?
- reflex movement of the eyes to vestibular stimulation
- Are vestibular projections to the cortex unilateral or bilateral? Ipsi or contralateral?
- bilateral, contralateral
- Where do vestibular projections to the cortex terminate?
- In the postcentral gyrus, just above the lateral fissure
- Where is the origin of the efferent vestibular system?
- from cells near the abducens nerve
- The efferent vestibular system projects ---laterally via the ----- nerve
- bilaterally, vestibular
- What 3 areas does the efferent vestibular system innervate?
- Hair cells in cristae of semicircular ducts
Hair cells in maculae of utricle and sacule
- Are the fibers of the efferent vestibular system excitatory or inhibitory?
- excitatory, trying ot match anticipated movement
- What are 4 clinical signs of vestibular dysfunction?
- What are the 2 parts of nystagmus?
- 1) Slow eye movement in opposite direction of head movement
2) Fast, saccadic compnent in opposite direction of slow eye movement (same direction as head turning)
- What is Meniere's syndrome?
- Overproduction of endolymph, causing auditory and vestibular disturbances
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