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60 Cards in this Set

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What are the 3 sources other than the cutaneous exteroceptors that the body uses to determine its position in space?
Eyes
Proprioceptive ending
Vestibular apparatus
What are the 2 subdivisions of the vestibular system?
Static labyrinth
Kinetic 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?
vertically
How is the macula oriented in the utricle?
horizontally
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?
Excitation
What happens when the hair cells are bent away from the kinocilium?
Inhibition
What is the function of the kinetic labyrinth?
Detection of angular acceleration
How many semicircular canals are in the kinetic labyrinth?
3
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?
Cristae
What is located in the cristae of the ampullae?
Hair cells
Where are the stereocilia of the hair cells embedded?
cupula
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?
inhibitory
What is the action of fibers from the fastigial nucleus from the cerebellum to the vestibular nuclei?
excitatory
Where does the vestibulospinal tract originate?
lateral vestibular nucleus
Does the vestibulospinal tract run ipsi or contralaterally?
ipsilaterally
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?
Nystagmus
dizziness
vertigo
vestibular ataxia
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