Vestibular Anatomy and Overview

Question 1

Vestibular system is located?

Answer 1

Deep in bilateral temporal bones

Question 2

Vestibular system is responsible for…

Answer 2

1. Awareness of body position in space
2. Maintaining postural control against gravity
3. Coordinating eye and head movements

Question 3

Primary functions of the vestibular system?

Answer 3

• Gaze stability (Vestibulo-ocular Reflex VOR)
• Postural stability (Vestibulo-spinal Reflex VSR)
• Orientation in space

Question 4

Peripheral Vestibular System is made up of what?

Answer 4

2 connected organs
- cochlea
- vestibular apparatus (labyrinth)

Question 5

Each vestibular apparatus consists of how many neural structures?

Answer 5

5 on each side (10 total)
- 3 semicircular canals
- 2 otolith organs (Utricle and Saccule)

Question 6

Horizontal canal is orientated how?

Answer 6

angled/tipped back 20-30 degrees

Question 7

Posterior canals are orientated how?

Answer 7

parallel with the ear lobe

Question 8

Anterior canal detects what type of motion?

Answer 8

It detects head rotation with forward motion

eg. reaching to the floor or preforming a forward roll

Question 9

Posterior canal detects what type of motion?

Answer 9

It detects posterior rotation of teh head

eg. looking overhead or moving from long sitting to supine

Question 10

Horizontal canal detects what type of motion?

Answer 10

It detects lateral rotation of the head

eg. looking right and left or rotating the body when upright

Question 11

What are the semicircular canals filled with?

Answer 11

Endolymph which has adensity slightly higher than water

Question 12

Endolymph moves freely within the canals as a response to what?

Answer 12

The direction of head rotation

Question 13

What is ampulla?

Answer 13

an enlargement on one end of each semicircular canal that the endolymph flows into
it is where the sensory hair cells lie

Question 14

What is a cupula?

Answer 14

flexible gelatinous barrier that can bend/sway that lies within each ampulla
contains cilia and converts the cupula movement into neural firing

Question 15

What are the “Functional Pairs” that are coplanar?

Answer 15

R/L Horizontal Canals
“LARP” - left anterior/right posterior
“RALP” - right anterior/left posterior

Question 16

What kind of signals are produced in each functional pair of the canal?

Answer 16

Reciprocal signals

eg. incraesed signals from the right canal occur simultaneously with decreased signals from its partner on the left side

Question 17

Acute disturbanceof SCC will result in?

Answer 17

Vertigo and imbalance

Question 18

Utricle and Saccule are sensitive to?

Answer 18

Linear acceleration and static head tilts (gravity sensitive)

NOT sensitive to head rotation

Question 19

Utricle sits in what plane and responds to what motion?

Answer 19

Horizontal plane

Responds to horizontal linear acceleration and/or lateral head tilt

eg. detecting forward/back motion while in a car

Question 20

Saccule sits in what plane and responds to what motion?

Answer 20

Vertical plane

Responds to vertical linear acceleration

eg. detecting up/down movements in an elevator

Question 21

Acute problems with otolith organs leads to…

Answer 21

Imbalance, sense of being shoved/pushed in one direction, or dizziness with linear acceleration

Question 22

What regions of the CNS make up the central vestibular system?

Answer 22

Cerebellum
Vestibulospinal tracts
Visual and occulomotor systems

Question 23

What is the function of the Central Vestibular System?

Answer 23

Takes information from the peripheral vestibular system and processes it to coordinate a motor output

Question 24

All ____ information received by the vestibular nuclei is shared and sent to the vestibular nuclei on the _____ side for integration of _____ information.

Answer 24

1. Afferent
2. Contralateral
3. Sensory

Question 25

Central Vestibular System nuclei work very closely with what what other part of the brain?

Answer 25

Cerebellum

helps with smoothness or movement

Question 26

How is information sent through the central verstibular system?

Answer 26

1. Distally through medial and lateral vestibuospinal tracts - to maintain postural stability -VSR-
2. To oculomotor nuclei (CV 3/4/5/) - to coordinate eye movements to allow for stable visual fixation during head movements -VOR-
3. To thalamus and cortex - for arousal and counscious awearness of the body and head in space

Question 27

Resting tonic firing rate

Answer 27

100 pulses/second

Question 28

What happens if there is damage to the tonic firing rate?

Answer 28

When damaged, there is asymmetry and that can lead to vertigo and nystagmus

eg. actue loss of function on right side vestibular nerve; brain thinks that you are turning left due to increased firing rate on the left side vs right

Question 29

What is VOR?

Answer 29

Vestibulo-ocular reflex

very fast reflex responsible for maintaining stability of an image during rapid head movements

Question 30

This eye movement is ____ and ____ to teh direction of the head movement.

Answer 30

Equal and opposite

Question 31

VOR - Phase

Answer 31

as head moves one direction, the eyes should move opposite direction at equal amplitude (distance)

eg. if head moves 10 degrees right , eyes move 10 degrees left

Question 32

VOR - Gain

Answer 32

as head moves on direction, the eyes move in the opposite direction with equal velocity

eg. if heads moves 10 degrees right at 100 degrees/second, eyes should move 10 degrees left also at 100 degrees/second

Question 33

Problems with VOR could lead to

Answer 33

problems with dynamic visual acuity

difficulty with fast head movements, quick turns, even driving

leads to dizziness, nausea, unsteadiness, and blurry vision with head movements

Question 34

Oscillopsia

Answer 34

blurred or bouncy vision with haed movement due to decraesed gaze

lack of coordination of how the eyes move within the head