Vestibular System

Front 1

What are the 3 sources other than the cutaneous exteroceptors that the body uses to determine its position in space?

Back 1

Eyes
Proprioceptive ending
Vestibular apparatus

Front 2

What are the 2 subdivisions of the vestibular system?

Back 2

Static labyrinth
Kinetic labyrinth

Front 3

What is the function of the static labyrinth?

Back 3

detection of linear acceleration and gravity

Front 4

What are the 2 parts of the static labyrinth?

Back 4

Saccule and utricle, both with macula

Front 5

What is located in the macula?

Back 5

Hair cells and otolithic membrane

Front 6

Describe the hair cells of the macula

Back 6

Cells with stereocilia whose "hairs" are embedded in the otolithic membrane and have a single rigid kinocilium

Front 7

Describe the otolithic membrane of the macula

Back 7

A gelatinous substance with embedded calcium carbonate particles. The "hairs" are embedded in it.

Front 8

What does the saccule connect with?

Back 8

The cochlear duct

Front 9

How is the macula oriented in the saccule?

Back 9

vertically

Front 10

How is the macula oriented in the utricle?

Back 10

horizontally

Front 11

What is the function of the utricle?

Back 11

Monitors acceleration and tilting of the head

Front 12

What are 2 actions that can displace the otolithic membrane?

Back 12

Linear acceleration of the head
Change in head position

Front 13

What happens when the otolithic membrane is displaced?

Back 13

Stereocilia that are embedded in the membrane bend, either towards or away from the kinocilium

Front 14

What happens when the hair cells are bent towards the kinocilium?

Back 14

Excitation

Front 15

What happens when the hair cells are bent away from the kinocilium?

Back 15

Inhibition

Front 16

What is the function of the kinetic labyrinth?

Back 16

Detection of angular acceleration

Front 17

How many semicircular canals are in the kinetic labyrinth?

Back 17

3

Front 18

What is the arrangement of the semicircular canals?

Back 18

perpendicular to each other

Front 19

What is the relationship of the anterior canal with the posterior canal of the opposite side?

Back 19

in line with it

Front 20

What is the relationship of the posterior canal with the anterior canal of the opposite side?

Back 20

in line with it

Front 21

What is the relationship of the lateral canal with the other canals?

Back 21

Horizontally, off by 30 degrees

Front 22

Where is the sensory portion of these canals?

Back 22

In a dilated portion called the ampulla

Front 23

What are the special receptor sites in the ampullae called?

Back 23

Cristae

Front 24

What is located in the cristae of the ampullae?

Back 24

Hair cells

Front 25

Where are the stereocilia of the hair cells embedded?

Back 25

cupula

Front 26

Flow of ---- caused by ----- acceleration of head causes displacement of ------ which results in stimulation of -----

Back 26

endolymph, angular, cupula, hair cells

Front 27

What are vestibular (Scarpa's) ganglion cells?

Back 27

biploar cells

Front 28

Where do the peripheral processes of vestibular ganglion cells synapse?

Back 28

hair cells of the vestibular apparatus

Front 29

What do the central processe of vestibular ganglion cells make up?

Back 29

vestibular portion of the vestibulocochlear nerve

Front 30

What are the 3 vestibular nuclei in the brainstem?

Back 30

Lateral vestibular nucleus (Dieter's)
Medial vestibular nucleus
Superior vestibular nucleus

Front 31

What does the lateral vestibular nucleus (Dieter's) form? Why is this important?

Back 31

Vestibulospinal tract, important in posture

Front 32

What does the medial vestibular nucleus form? Why is this important?

Back 32

Contributes to the medial longitudinal fasiculus, important in vestibulo-occular reflexes

Front 33

Where do the superior and inferior vestibular nuclei project to? What is their function?

Back 33

Cerebellum, integration and modulation of posture

Front 34

Some vestibular fibers terminate directly in the ---- as ---- fibers

Back 34

archicerebellum, mossy

Front 35

Where do vestibular afferents terminate?

Back 35

Vestibular nuclei

Front 36

What are the 2 pathways that the vestibular nuclei have connections from the cerebellum?

Back 36

Direct Purkinje cell axons
Fibers from fastigial nucleus

Front 37

What is the action of direct Purkinje cells from the cerebellum to the vestibular nuclei?

Back 37

inhibitory

Front 38

What is the action of fibers from the fastigial nucleus from the cerebellum to the vestibular nuclei?

Back 38

excitatory

Front 39

Where does the vestibulospinal tract originate?

Back 39

lateral vestibular nucleus

Front 40

Does the vestibulospinal tract run ipsi or contralaterally?

Back 40

ipsilaterally

Front 41

Where in the spinal cord does the vestibulospinal tract run?

Back 41

all levels

Front 42

where do the vestibulospinal tract fibers synapse?

Back 42

Verntral horn cells

Front 43

What is the action of vestibulospinal tract fibers?

Back 43

excite extensors

Front 44

Why is the vestibulospinal tract important?

Back 44

postural adjustments to vestibular stimulation

Front 45

What are the 2 subdivisions of the median longitudinal fasiculus?

Back 45

descending and ascending limb

Front 46

Where does the descending limb of the MLF originate?

Back 46

all vestibular nuclei, but particularly the medial

Front 47

Where in the spinal cord does the descending limb of the MLF run to?

Back 47

bilaterally to cervical spinal cord

Front 48

Where do the fibers of the descending limb of the MLF synapse?

Back 48

Ventral horn cells

Front 49

What is the function of the descending limb of the MLF?

Back 49

Reflex turning of the head to vestibular stimulation

Front 50

Where do the fibers of the ascending limb of the MLF have inputs to?

Back 50

abducens, trochlear, and occulomotor nuclei

Front 51

What is the function of the ascending limb of the MLF?

Back 51

reflex movement of the eyes to vestibular stimulation

Front 52

Are vestibular projections to the cortex unilateral or bilateral? Ipsi or contralateral?

Back 52

bilateral, contralateral

Front 53

Where do vestibular projections to the cortex terminate?

Back 53

In the postcentral gyrus, just above the lateral fissure

Front 54

Where is the origin of the efferent vestibular system?

Back 54

from cells near the abducens nerve

Front 55

The efferent vestibular system projects ---laterally via the ----- nerve

Back 55

bilaterally, vestibular

Front 56

What 3 areas does the efferent vestibular system innervate?

Back 56

Hair cells in cristae of semicircular ducts
Hair cells in maculae of utricle and sacule

Front 57

Are the fibers of the efferent vestibular system excitatory or inhibitory?

Back 57

excitatory, trying ot match anticipated movement

Front 58

What are 4 clinical signs of vestibular dysfunction?

Back 58

Nystagmus
dizziness
vertigo
vestibular ataxia

Front 59

What are the 2 parts of nystagmus?

Back 59

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)

Front 60

What is Meniere's syndrome?

Back 60

Overproduction of endolymph, causing auditory and vestibular disturbances