Vestib: Peripheral Anatomy

Question 1

List the vestibular symptoms that impact function

Answer 1

• Dizziness
• Vertigo
• Imbalance
• Visual fatigue/blurring
• Headache

Question 2

What is the prevalence of dizziness?

Answer 2

*#1 complaint for those over 65
*42% of people describe feeling of dizziness in their lifetime
*85% of dizziness is peripheral

Question 3

What is the purpose of the vestibular system?

Answer 3

1. Allows for maintenance of gaze stability with head movement such as the detection of head angular velocity and linear acceleration
2. Provides reflexive information for maintaining upright posture to help orient the head and body to gravity
3. Support the spatial perception and orientation of the body

Question 4

What is order of convergence for sensory input?

Answer 4

1. Sensory
2. Integration
3. Motor input
4. Balance

Question 5

What falls under sensory inputs?

Answer 5

1. Vestibular
2. Visual
3. Proprioceptive

Question 6

What falls under integration of input?

Answer 6

1. Cerebellum
2. Cerebral Cortex
3. Brainstem

Question 7

What falls under motor input?

Answer 7

1. Vestibulo-ocular reflex
2. Motor impulses for eyes
3. Motor impulses for postural adjustments

Question 8

What are the two labyrinths in the cochlea?

Answer 8

1. Bony
2. Membranous

Question 9

What is the SSCs covered in?

Answer 9

Bony labyrinth

Question 10

Which structures of the vestibular system is housed within the membranous labyrinth?

Answer 10

1. Perilymph
2. Endolymph
3. SSCs duct
4. Ampullae

Question 11

The membranous portion suspend into ___ and it is filled with _____

Answer 11

Perilymph & Endolymph

Question 12

What are the peripheral boundaries:

1. OE: ____ to ___
2. ME: ____ to ___
3. IE: ____ to __

Answer 12

1. Pinna to TM
2. TM to Oval window (stapes)
3. Oval window to VIIIth nerve

Question 13

What are the vestibular End-organs?

Answer 13

1. 3 SSCs
2. 2 otoliths

Question 14

What are the central processors?

Answer 14

1. Brainstem
2. Cerebellum

Question 15

What does the vestibular apparatus house?

Answer 15

1. Utricle
2. Saccule
3. SSCs ducts

Question 16

List the orientation of the 3 SSCs and their degrees

Answer 16

1. Anterior/Superior = Sagittal Plane (Nodding) – 45
2. Horizontal/Lateral = Transverse Plane (rotating) – 30
3. Posterior/Inferior = Frontal plane (bending) – 45

Question 17

Which liquid is the ampulla, crista ampullaris, and cupula housed in?

Answer 17

Endolymph

Question 18

What is the pairing of the contralateral SSCs duct when they are oriented in the same plane?

Answer 18

1. Right Superior –> Left Posterior
2. Left Superior –> Right Posterior
3. Left Horizontal –> Right Horizontal

LARP v RALP

Question 19

For the SSCs, where are the HCs embedded?

Answer 19

Cupulla

Question 20

List the process for when the HCs bends in the opposite direction of rotation & linear.

Answer 20

1. Ion channels open
2. HCs depolarize and increase the firing of afferent fibers
3. Rotational velocity equalizes and the cupula is back to an upright position
4. The membrane potential of the cell normalizes

Question 21

List the process for when the HCs bends in the same direction of rotation and linear.

Answer 21

1. Ion channel closes
2. HCs hyperpolarized and causes a decrease in reduction of the afferent nerve firing
3. Cupula is back in upright position
4. Membrane equalizes

Question 22

What does Type I HC focus on?

Answer 22

Phasic; fires when moving

Question 23

What does Type II HC focus on?

Answer 23

Tonic; fires all the time to help us know where we are in space

Question 24

What does the SSC stimulation detects?

Answer 24

Angular velocity of the head

Question 25

What are some advantages of the SSC stimulation?

Answer 25

1. Allows for sensory redundancy if a pathology of one of the SSC duct occurs 2. "Common mode rejection" - the simultaneous firing of both SSC ducts of the pair is ignored by the CNS 3. Phsyiologic layout allows for compensation for sensory overload

Question 26

What are the divisions of the vestibular nerve and where does each division send information to?

Answer 26

1. Superior Branch = Utricle, Horizontal & Anterior SCCs 2. Inferior Branch = Saccule & Posterior SCC

Question 27

Where does the vestibulocochlear travel past?

Answer 27

Cerebellopontine angle

Question 28

Where does the vestibulocochlear travel enter into?

Answer 28

Brainstem at pontomedullary junction

Question 29

What is the resting firing rate of the vestibular nerves?

Answer 29

70-100Hz

Question 30

When excited, what happens with the hair cells?

Answer 30

They bend towards the kinocilium and firing rate increases

Question 31

When inhibited, what happens to the hair cells?

Answer 31

Bend away from kinocilium and firing rate decreases

Question 32

What are the primary output centers of the central processing of the vestibular input?

Answer 32

1. Vestibular Nuclear Complex 2. Cerebellum

Question 33

Where is the Vestibular Nuclear Complex (VNC) located?

Answer 33

Rostral medulla and caudal pons

Question 34

What is the role of the VNC?

Answer 34

Relay center for vestibular information

Question 35

List the four VN’s and where they project to

Answer 35

1. Lateral VN = Utricle & Saccule 2. Superior VN + Medial VN = SCCs 3. Inferior/Dorsal = Other nuclei + Saccule

Question 36

Explain velocity storage system

Answer 36

Is when the CNS converts the small time constant response at the canal afférents to the long time constants response found at the level of the VN If it extends 5.7s there’s disequilibrium in the system if the energy stored is not the same