Vestibular System

Question 1

What is the main function of the vestibular system

Answer 1

• Responsible for maintaining our balance, posture and spatial orientation

Question 2

what are the 3 receptor systems that the vestibular system integrates

Answer 2

• The eyes
• General proprioceptive(muscle, joints and tendons) and cutaneous receptors
• Vestibular receptors in the inner ear (the vestibular apparatus)

Question 3

what is the inner ear made out of

Answer 3

• The labyrinth
• Vestibular apparatus
• Cochlear

Question 4

What are the two types of fluid within the labyrinth

Answer 4

• endolymph

- perilymph

Question 5

what is the difference between the endolymph and perilymph

Answer 5

Endolymph
- High in potassium low in sodium

Perilymph
- Low in potassium high in sodium

• this allows the vestibular cells to function and establish the end-cochleae potential

Question 6

what is the labyrinth divide into

Answer 6

The labyrinth contains an auditory part and a vestibular par

Question 7

What is present the vestibular part of the labyrinth

Answer 7

In the vestibular part, there are 3 semicircular ducts (posterior, anterior and lateral)
- these lie 90 degrees to each other

Question 8

what activates the cells int he semicircular ducts

Answer 8

Movement of endolymph inside may activate the cells in the duct, depending on the position of the head.

Question 9

what is also present in the vestibular part

Answer 9

there is also the utriculus and the sacculus.

Question 10

What are present in the utriculus and sacculus

Answer 10

Present in these are small protrusions where the vestibular cells lie.

Question 11

what do vestibular cells have

Answer 11

The vestibular cells have many cilia(stereocilia and kinocilia), which depending on movement cause hyperpolarisation or depolarisation of the cell by releasing glutamate.

Question 12

What is present in the ampulla

Answer 12

Inside the ampulla, there is a gelatinous substance called the cupula where the cilia are embedded.

Question 13

movement of the cupola….

Answer 13

causes movement of the cilia

Question 14

what is the difference between the ampulla, utricular and saccule

Answer 14

In the ampulla there is cupola which embeds the cilia whereas In the utricular and saccular maculae, there are also cilia cells but they are slightly different due to the presence of otoconia (calcium crystals which provide gravitational stimulation).

Question 15

what do the hair cells of the articles and saccule work together to produce

Answer 15

The hair cells of the utricles and saccule work together to provide a 3-dimensional representation of direction of linear force.

Question 16

describe the difference between the trickles and saccule

Answer 16

In the utricles, hair cells are polarized (excited) towards the striola. Provides horizontal encoding.

In the saccules, hair cells are polarized away from the striola

Question 17

What are striola

Answer 17

• narrow central area of the utricular macula where the orientations of the tallest stereocilia and kinocilia change).
• Provides vertical encoding.

Question 18

describe how the vestibular-ocular reflex and nystagmus is activated

Answer 18

Activation of vestibular cells —> activation of vestibular neurones —> extraocular motor neurones —> eye muscles —> compensatory eye movements to fix a visual target (opposite to the direction of movement)

Question 19

name the 4 vestibular nuclei

Answer 19

superior, medial, lateral and descending vestibular nucle

Question 20

describe where signals from the labyrinth go

Answer 20

From the labyrinth, afferent signals enter the 4 vestibular nuclei (superior, medial, lateral and descending vestibular nuclei). Signals then reach 3 major destinations and 1 important destination.

• Spinal cord through the vestibulospinal tract
• Reticular formation
• Superior colliculus and eye muscle nuclei
• Medial cerebellar nucleus to control balance (see diagram in more detail showing flocculonodular lobe).

Question 21

what are the efferent outputs for the labyrinth

Answer 21

• Spinal cord through the vestibulospinal tract
• Reticular formation
• Superior colliculus and eye muscle nuclei
• Medial cerebellar nucleus to control balance (see diagram in more detail showing flocculonodular lobe).

Question 22

what is kinetosis

Answer 22

disagreement exists between visually perceived movement and the vestibular system’s sense of movement.

Question 23

What is meunière disease

Answer 23

a disease of unknown cause affecting the membranous labyrinth of the ear, causing progressive deafness and attacks of tinnitus and vertigo.

Question 24

what is benign paroxysmal positional vertigo

Answer 24

one of the most common causes of vertigo — the sudden sensation that you’re spinning or that the inside of your head is spinning.

• Within the labyrinth of the inner ear lie collections of calcium crystals known as otoconia or otoliths.
• In patients with BPPV, the otoconia are dislodged from their usual position within the utricle, and migrate over time into one of the semicircular canals.
• Dislodging the otoconia (‘ear rocks’) causes abnormal endolymph fluid displacement and a resultant sensation of vertigo.

Question 25

describe how to do the hall pike manoeuvre

Answer 25

• Patient sitting, turn head 45 degrees to face you and observe patients eyes for 30 seconds.
• The clinician helps the patient to lie down backwards quickly, with the patients head hanging off slightly from the bed.
• The patient’s eyes are then observed for about 45 seconds as there is a characteristic 5–10 second period of before the onset of nystagmus.

Question 26

What are the symptoms of vestibular issues

Answer 26

• Nystagmus
• Nausea
• Dizziness
• Disequilibrium
• Vertigo

Question 27

What are the causes of vestibular issues

Answer 27

• Nerve/inner ear infections
• Tumours
• Vascular insufficiency
• Trauma
• Endolymph imbalance

Question 28

How do you test for balance disorders

Answer 28

• Eye movements
• Claroic testsing
• Hallpike manoeuvre

Question 29

Name tests for the vestibular

Answer 29

(1) Videonystagmography
(2) Electronystography (ENG)
(3) Posturography, Bárany chair