Vestibular System

Question 1

What is the vestibular system responsible for?

Answer 1

Maintaining our balance, posture and spatial orientation.

Question 2

What three receptor systems does the vestibular system integrate?

Answer 2

The eyes
General proprioceptive and cutaneous receptors
Vestibular receptors in the inner ear

Question 3

What composes the inner ear?

Answer 3

The labyrinth, vestibular apparatus and cochlea

Question 4

What two types of fluid are in the labyrinth? How do they differ in concentration of potassium and sodium?

Answer 4

Perilymph (low potassium, high sodium)

Endolymph (high potassium, low sodium)

Question 5

What ducts does the vestibular part of the labyrinth have? What are the three other parts?

Answer 5

Semi-circular

Ampullae, utriculus and sacculus (the receptor cells are located here)

Question 6

What cells in the ampulla detect movement? What is their purpose?

Answer 6

Hair cells (kinocilia) - they have kinetic sensitivity, they are sensitive to head rotation, and angular acceleration.
They cause either depolarisation or hyper-polarisation depending on the direction of movement (away from the afferent nerve fibres for depolarisation).

Question 7

What is the role of the endolymph in sensing head movement?

Answer 7

If the head moves one way, the endolymph moves in the opposite direction, which bends the cupula with it (the cupula contains the cilia and hair cells).

Question 8

Where are the otoconia?

Answer 8

In the utriculus and sacculus

Question 9

What are utricles?

Answer 9

Hair cells are polarized (excited) towards the striola (divides each macula into medial and lateral halves) HORIZONTAL ENCODING

Question 10

What are saccules?

Answer 10

Hair cells are polarized away from the striola (divides each macula into anterior and posterior halves)
VERTICAL ENCODING

Question 11

What do the hair cells of the utricles and saccules work together to do?

Answer 11

Provide a three dimensional representation of the direction of linear force. They sense the tilt of the head, as well as gravity.

Question 12

What type of organs are saccule and utricle?

Answer 12

Otolithic

Question 13

What is the vestibulo-ocular reflex?

Answer 13

Activation of the vestibular system causes eye movement in order to stabilize images on the retinas during head movement. This is done by producing eye movements in the direction opposite to head movement.

Question 14

What is nystagmus?

Answer 14

Involuntary eye movements due to damage to vestibular apparatus, brainstem or cerebellum.

Question 15

Cristae for ____ changes, maculae for ____ changes.

Answer 15

Rotational

Linear

Question 16

VESTIBULO-OCULAR REFLEX - what is the pathway?

Answer 16

Vestibular nerve afferents –> central vestibular neuron –> extra-ocular motor neurons –> eye muscles

Question 17

What vestibular nuclei are there? Where are they?

Answer 17

Superior, medial, lateral and inferior/descending - next to cerebellum/pons.

Question 18

Where are the inputs from to the vestibular nuclei? Where do the outputs go?

Answer 18

From the vestibular apparatus and anterior lobe of cerebellum
To vestibulospinal tract and to eye muscle nuclei

Question 19

What centre does the reticular formation have relevant to the eyes?

Answer 19

Gaze

Question 20

The sense of equilibrium depends on signals coming from where? What does this record?
This must continuously be related to the positions and movements of the eyes and the body.

Answer 20

Vestibular apparatus - the position and movements of the head.

Question 21

Signals from vestibular receptors contribute to our conscious awareness of…?

Answer 21

The position of the body in space

Question 22

Name three peripheral vestibular pathologies.

Answer 22

Kinetosis (motion sickness)
Meniere’s disease
Benign paroxysmal positional vertigo (BPPV)

Question 23

What causes BPPV?

Answer 23

This causes dizziness due to damaged (i.e. by head injury, infection, age) otoconia from the utricle being displaced.

Question 24

How do you test for BPPV?

Answer 24

Hallpike manoeuvre (watch for nystagmus/if they get dizzy). Affected ear is pointed to the floor.

Question 25

What are the symptoms of peripheral vestibular pathologies? (5)

Answer 25

Nystagmus
Nausea
Dizziness
Disequilibrium
Vertigo

Question 26

What are the causes of peripheral vestibular pathologies? (5)

Answer 26

Nerve/inner ear infections
Tumours
Vascular insufficiency
Trauma 
Endolymph imbalance