Vestibular System

Question 1

What are 3 of the functions of the peripheral and central vestibular system that allow for maintenance of equilibrium?

Answer 1

1. Estimates body position and movement.
2. Postural control
3. Control of eye movements

Question 2

Where does the vestibular system project information to?

Answer 2

Sends projections throughout the cortex, brainstem, and cerebellum.

Question 3

What are 2 other functions of the vestibular system that allow for maintenance of equilibrium?

Answer 3

Autonomic function and consciousness

Question 4

What are the 3 primary functions of the peripheral vestibular system?

Answer 4

1. Stabilize visual image on fovea of retina during head movement to allow for clear vision.
2. Maintain postural stability, especially during movement of head.
3. Provide information for spatial orientation.

Question 5

What kind of information does the peripheral vestibular system relay?

Answer 5

Static and dynamic positions of head and neck.

Question 6

What is included in the bony labyrinth?

Answer 6

Perilymphatic fluid and supportive connective tissue. (protective structures)

Question 7

What are the components of the membranous labyrinth?

Answer 7

1. Vestibule

2. 3 semicircular canals

Question 8

Describe what is found within the vestibule.

Answer 8

Otolith organs

• Utricle
• Saccule

Question 9

What are the 3 semicircular canals?

Answer 9

1. Anterior semicircular canal
2. Posterior semicircular canal
3. Horizontal semicircular canal

Question 10

What kind of information do otolith organs relay?

Answer 10

Information about linear acceleration/ deceleration of head/neck and static head position.

Question 11

What type of motion does the utricle detect?

Answer 11

Movements in the horizontal plane.

Question 12

What type of motion does saccule detect?

Answer 12

Movement in vertical plane.

Question 13

What are sterocilia?

Answer 13

Motion receptors that transduce minute displacement into behaviorally relevant potentials.

Question 14

Describe the general presentation of sterocilia.

Answer 14

• Hair cells encased in gelatinous layer (macula)
• Gravity dependent motion sensitivity
• Has otoconia layered on top, which are calcium carbonate crystals.

Question 15

What are the 2 sterocilia found within the otolith organ?

Answer 15

Kinocilium = tallest fiber; its position determines excitatory or inhibitory response.

Stereocilia = all other hair fibers

Question 16

Describe if movement of the sterocilia towards or away from the kinicilium will be excitatory or inhibitory.

Answer 16

Movement of sterocilia towards kinocilium = excitatory

Movement of sterocilia away from kinocilium = inhibitory

Question 17

What helps amplify the movement of the sterocilia?

Answer 17

The otoconia and its calcium carbonate crystals. It makes it heavier than the structures it overlays.

Question 18

Describe what happens to the otolith organs during a forward or backward head tilt and with forward acceleration and deceleration.

Answer 18

Forward head tilt = tilt anteriorly

Backward head tilt = tilt posteriorly

Forward acceleration = posterior movement

Deceleration = Anterior movement

Question 19

What is the positioning of the utricle?

Answer 19

Positioned in the anterior and lateral planes.

Question 20

What is the positioning of the saccule?

Answer 20

Positioned in the superior and anterior planes.

Question 21

What type of movement does the semicircular canals relay info about?

Answer 21

Angular velocity of head.

Question 22

What encases the semicircular canals?

Answer 22

A bony labyrinth, filled with fluid called endolymph.

Question 23

Describe what happens within the semicircular canal to get an excitatory or inhibitory response.

Answer 23

Head rotation –> movement of endolymph in corresponding canal –> movement of hair cells in ampulla –> depolarization/hyperpolarization.

Question 24

Describe what an ampulla is.

Answer 24

Bulbous formation at the start or finish of each canal.

Contains cupula, which houses sterocilia.

Question 25

What kind of movement is the ampulla sensitive to?

Answer 25

Angular movements!

Question 26

Describe the positioning of the semicircular canals.

Answer 26

All positioned 90 degrees from one another. Anterior and posterior canals = 45 degrees off midline Horizontal canal = 30 degrees off horizontal plane

Question 27

Describe the pairing of the semicircular canals.

Answer 27

Anterior and posterior canals paired together. Horizontal canals paired together.

Question 28

What is the function of the vestibulo-occular reflex (VOR)?

Answer 28

Three neuron arc that allows for image stabilization when the head is moving. Results in eye movements that equally counter head movement.

Question 29

What makes up the central vestibular system?

Answer 29

Vestibular (internal reference) + visual somatosensory (external references) = central vestibular system.

Question 30

What are the functions and information relayed by vestibular nuclei?

Answer 30

1. Eye movement control for gaze stability during movement (occulomotor) 2. Postural control and movement (brainstem) = aid in maintaining muscle tone 3. Spatial orientation (cortex) 4. Autonomic nervous system control.

Question 31

What is the general function of the vestibular subnuclei?

Answer 31

Nuclei receive input from peripheral vestibular system, vision and somatosensory afferents.

Question 32

What are the 4 sets of subnuclei?

Answer 32

1. Lateral (dieter's) nucleus 2. Medial nucleus 3. Superior nucleus Inferior nucleus

Question 33

What is the role of the lateral (Dieter's) nucleus?

Answer 33

- Outputs info to the cerebellum for feedback. - - Outputs to lateral vestibulospinal tract to facilitate extensors (posture; muscles of trunk and legs)

Question 34

What is the role of the medial nucleus?

Answer 34

Providesd descending output to muscles of head and neck via medial longitudinal fasciculus (MLF; head position)

Question 35

What is the role of the superior nucleus?

Answer 35

Provides ascending output (via MLF) to oculomotor nuclei (CN 3, 6; VOR)

Question 36

What is the role of the inferior nucleus?

Answer 36

- Outputs to the cerebellum (feedback) - Outputs to the reticular formation (arousal and ANS) - Outputs to the oculomotor nuclei (CN 3, 4, 6; VOR)

Question 37

Where does the lateral vestibulospinal tract travels and what information does it carry?

Answer 37

Travels to the thoracic spinal cord to extensor muscles to relay information about: - Head and body position in space - Walking upright - Righting and equilibrium reactions.

Question 38

Where does the medial vestibulospinal tract | travel and what information does it carry?

Answer 38

Travels to the cervical spinal cord to extensor musculature to relay info about: - Head movements - Integrating head and eye movements.

Question 39

What is the vestibulocerebellum in charge of?

Answer 39

Responsible for postural and gaze stabilization: - modulates VOR - provides and receives feedback from postural muscles on balance and equilibrium.

Question 40

Is there a primary vestibular cortex?

Answer 40

Heckin no!

Question 41

Where is the parieto-insular vestibular cortex (PIVC) found and what information does it recieve?

Answer 41

Found at junction of parietal and insular lobe. Receives input from the cerebellum and vestibular nuclei via the thalamus (visual, somatosensory and vestibular integration)

Question 42

What is an optokinetic nystagmus?

Answer 42

Quick back and forth movement of the eyes.

Question 43

What kind of information is integrated and perceived in the medial superior temporal region

Answer 43

- visual vestibular integration | - self motion perception

Question 44

What kind of information is integrated in the ventral intraparietal region?

Answer 44

- Spatial orientation | - Proprioception, auditory, visual, tactile, vestibular integration