The Vestibular System

Question 1

What is the function of the vestibular system?

Answer 1

Balance, posture and spatial orientation by integrating eyes, general proprioception and cutaneous receptors in addition to inner ear

Question 2

What is the fluid composition of the endolymph compared to the perilymph in the vestibular system?

Answer 2

Endolymph = high K+ and low Na+
Perilymph = low K+ and high Na+ (same as CSF)

Question 3

What are the hair cells in the semicircular canals (ampulla cristae) sensitive to?

Answer 3

Kinetic sensitivity
Head rotation
Angular acceleration
Complementary bilateral signalling

Question 4

What are the hair cells in the saccule and utricle (otolithic organs) sensitive to?

Answer 4

Utriculus - horizontal and sacculus - vertical
Gravity
Tilt of head
Linear acceleration

Question 5

What is angular acceleration?

Answer 5

Quantitative expression of the change in angular velocity that a spinning object undergoes per unit of time

Question 6

What is linear acceleration?

Answer 6

The rate of change of velocity without a change in direction

Question 7

How do mechanoreceptors in the vestibular apparatus signals change?

Answer 7

When cilia bends –> receptor K+ channel opens –> glutamate release –> vestibular nerve fibres

Question 8

What is nystagmus?

Answer 8

A vestibular-ocular reflex which involves an initial slow rotation followed by a fast flick-back

Question 9

What is kinetosis?

Answer 9

Motion sickness

Question 10

How do you test for benign paroxysmal positional vertigo (BPPV)?

Answer 10

1. Lower head to the table and turn to one side.
2. Watch eyes for nystagmus.
3. If patient gets dizzy & exhibits nystagmus, the ear pointed to the floor is the affected ear.
4. If nothing happens, repeat test on the other side to check the other ear.
5. The person is then moved back to the upright position.