Vestibular A&P

Question 1

What are the major functions of the vestibular system?

Answer 1

• Estimate body position and movement
• Postural control
• Control eye movement related to head movement
• Autonomic function and consciousness

Question 2

What is the peripheral nervous system tasked with as it relates to vestibular function?

Answer 2

• Stabilize images during head movement to allow for clear vision
• Maintain postural stability esp during movement of head
• provide information for spatial orientation

Question 3

What is inside the bony labyrinth?

Answer 3

perilymphatic fluid and supportive connective tissue

Question 4

What is the purpose of the bony labyrinth?

Answer 4

protection and communication with CFS via cochlear aqueduct

Question 5

What lies within the vestibular labyrinth?

Answer 5

bony and membranous labyrinths

Question 6

What is inside the membranous labyrinth?

Answer 6

Endolymph fluid, vestibule, and semicircular canals

Question 7

What lies within the vestibule?

Answer 7

otolith organs: utricle and saccule

Question 8

What is the function of the otolith organs?

Answer 8

relay info about linear acceleration/deceleration of head/neck + static head position

Question 9

Utricle detects movement in the ________ plane.

Answer 9

horizontal

Question 10

Saccule detects movement in the _______ plane.

Answer 10

vertical

Question 11

Otolith organs are _________ to gravity

Answer 11

relative

Question 12

How do otolith organs detect movement?

Answer 12

movement relative to gravity is detected by the movement of sterocilia/kinocilium; otoconia increase the sensitivity of the movement.

Question 13

Movement of stereocilia TOWARD kinocilium is _______ (what movement of head?)

Answer 13

excitatory (backward tilt/forward acceleration)

Question 14

Movement of stereocilia AWAY from kinocilium is ________ (what movement of head?)

Answer 14

inhibitory (forward tilt/backward acceleration)

Question 15

How do otoliths achieve full spatial representation with regard to movement detection?

Answer 15

positioning of kinocilium and stereocilia provides complete representation for all planes of movement

Question 16

What is the function of the semi-circular canals?

Answer 16

relay info about angular velocity of head

Question 17

Are the semicircular canals typically gravity independent or dependent?

Answer 17

Gravity independent

Question 18

What is the ampulla and what is it’s functional relevance?

Answer 18

bulbous formation at the start/end of each canal

Houses the cupula which holds the stereocilia

Question 19

Explain the relevance to the directional flow of endolymph fluid in the semicircular canals.

Answer 19

head movement > movement of endolymph in corresponding canal > movement of hair cells in ampulla > depolarization/hyperpolarization

Question 20

Utriculopedal

Answer 20

movement of endolymph toward the utricle

“pedal towards your destination”

Question 21

Utriculofugal

Answer 21

movement of endolymph away from the utricle

“Frugal = stay away from spending”

Question 22

Utriculopedal is excitatory for the ____ canal and inhibitory for the ____ canal

Answer 22

Utriculopedal is excitatory for the HORIZONTAL canal and inhibitory for the ANTERIOR/POSTERIOR canal

Question 23

Utriculofugal is excitatory for the ____ canal and inhibitory for the ____ canal

Answer 23

Utriculofugal is excitatory for the ANTERIOR/POSTERIOR canal and inhibitory for the HORIZONTAL canal

Question 24

Explain how the R/L semicircular canals are paired. What movment is each canal most sensitive too?

Answer 24

R + L horizontal canals (30º head tilt + turning L/R)
R anterior + L posterior (45º from midline R, “yes” motion)
L anterior + R posterior (45º from midline L, “yes” motion)

Question 25

What is the major source of vascularization for the vestibular system?

Answer 25

Labyrinthine artery off the AICA

Question 26

What are the two branches of the labyrinthine artery and main areas they supply?

Answer 26

- Anterior vestibular a. (vestibular n., utricle, ampullae of anterior and horizontal SCC) - Common Cochlear a. (cochlea, ampulla of posterior SCC, saccule)

Question 27

What are the 3 main vestibular reflexes?

Answer 27

- Vestibulo-ocular reflex (VOR) - Vestibulospinal Reflex (VSR) - Vestibulocollic Reflex (VCR)

Question 28

Vestibulo-ocular reflex (VOR)

Answer 28

generates eye movements that enable clear vision while head is in motion

Question 29

Vestibulospinal Reflex (VSR)

Answer 29

Generates compensatory body movement to maintain head and postural stability.

Question 30

Vestibulocollic Reflex (VCR)

Answer 30

Acts on neck musculature to stabilize head.

Question 31

How is normal VOR quantified?

Answer 31

Normal VOR Gain = -1

Question 32

Vestibulospinal Reflex (VSR)

Answer 32

- head tilts to side - Ipsi. SCC/otolith excitation - ↑ input from vestibular nerve > vestibular nuclei ipsilaterally - MVST/LVST descending drive to truncal muscles. - ↑ lateral truncal extension **ipsilaterally**/↑ truncal flexion **contralaterally**

Question 33

Three Cervical Reflexes

Answer 33

- Cervico-ocular reflex (COR) - Cervicospinal Reflex (CSR) - Cervicocollic Reflex (CCR)

Question 34

Cervico-ocular reflex

Answer 34

- Interacts closely with VOR - Eye movements driven by neck proprioceptors

Question 35

Cervicospinal reflex

Answer 35

Changes in limb position drive by neck afferent activity

Question 36

Cervicocollic Reflex

Answer 36

Helps stabilize head on body, changes in neck position = afferent input > contralateral reflexive contraction of appropriate neck muscles

Question 37

What is the general purpose of the cervical reflexes?

Answer 37

They supplement the vestibular reflexes

Question 38

What is the function of the central vestibular system?

Answer 38

relays information about: - eye movement control for gaze stability during movement. (oculomotor) - Postural control and movement (brainstem) - Spatial orientation (cortex) - Autonomic nervous system control

Question 39

What are the four vestibular nuclei?

Answer 39

- Lateral nucleus - Medial nucleus - Superior nucleus - Inferior nucleus

Question 40

Lateral Nucleus function

Answer 40

Prinicple vestibular relay

Question 41

Medial nucleus

Answer 41

VOR/VSR relay

Question 42

Superior Nucleus

Answer 42

VOR relay

Question 43

Inferior Nucleus

Answer 43

Cerebellar and reticular formation relay

Question 44

Function of the lateral vestibulospinal tract.

Answer 44

- Head and body position in space. - Walking upright - Righting and equilibrium reactions ## Footnote PONS > thoracic spinal cord to extensor musculature

Question 45

Function of Medial Vestibulospinal tract

Answer 45

- Head movements - Integrating head and eye movementa ## Footnote Medulla > cervical spinal cord extensor musculature

Question 46

How is the cerebellum involved in vestibular function?

Answer 46

- VOR/VSR suppression (Flocculonodular node) - Vestibulocerebellar tract: error correcting mechanism, intended v. actual movement - Cerebellar-Cortical Loop: adaptation of postural responses based on prior experiences (*lynx, airport walkways*)

Question 47

What cortical areas are associated with vestibular function? What are each of their functions?

Answer 47

- Parieto-Insular Vestibular Cortex: PIVC - Medial Superior Temporal Region - Ventral Intraparietal Region

Question 48

Parieto-Insular Vestibular Cortex (PIVC) function

Answer 48

Receives input from cerebellum and vestibular nuclei via the thalamus about visual, somatosensory, and vestibular integration.

Question 49

Medial Superior Temporal Region Function

Answer 49

- Visuo-vestibular integration - Self-motion perception

Question 50

Ventral Intraparietal Region Function

Answer 50

- Spatial orientation - Proprioceptive, auditory, visual, tactile, vestibular integration