The Vestibular System

Question 1

What are the 3 structures which make up the vestibular apparatus?

Answer 1

Semicircular canals (3)
Utricle (2 sac like swellings)
Saccule

Question 2

The vestibular system is a series of endolymph-filled, membranous tubes that connect with …

Answer 2

The cochlear duct

Question 3

What do the semicircular canals detect?

Answer 3

Angular acceleration during rotation of the head along 3 perpendicular axis
(Nodding ‘yes’
Shaking ‘no’
Tipping to shoulder)

Question 4

Receptor cells of the semicircular canals have hair cells covered in a gelatinous mass, the …

Answer 4

Cupula

Question 5

What is the ampulla?

Answer 5

A slight bulge in the wall of each semicircular canal

Question 6

What causes bending of the stereocilia in the vestibular system?

Answer 6

Head moves.
Causes the hair cells & bony enclosure to move too.
Fluid stays stationary due to inertia.
Ampulla is pushed against the stationary fluid
= bending of the stereocilia & alteration in the release of neurotransmitter

Question 7

How is the speed and magnitude of rotational head movements determined?

Answer 7

• Neurotransmitter is released from the hair cells at rest.
• Increases/decreased according to the way that the stereocilia are bent
• Each cell has a direction of maximum neurotransmitter release which depolarises the cell. The cell is hyperpolarized when in the opposite direction.

Question 8

What do the utricle and the saccule provide information about?

Answer 8

Linear (up, down & back, forth) acceleration and changes in head position relative to gravity

Question 9

How is vestibular information used?

Answer 9

1. Control eye muscles so eyes can remain on a fixed point in spite of head movements.
2. Reflex mechanisms to maintain upright posture and balance
3. To provide conscious awareness of position and acceleration of the body, perception & memory of space around the body.