Topic 9 - the vestibular system

Question 1

What is the vestibular system?

Answer 1

system for balance and spatial orientation.

• keeps eyes still as as we move
• maintaines upright posture.

Question 2

In the vestibular system, what is the vestibular labyrinth filled with?

Answer 2

filled with endolymph = high potassium fluid.

Question 3

what cells are the sensory receptors of the vestibular system>?

Answer 3

Hair cells - just like in the auditory system but they respond to lower frequencies of 0-20Hz.

Question 4

Why is the vestibular hair bundle structurally different to that of auditory hair cells?

Answer 4

Vestibular hair cells keep their kinocilium throughout life

There are 2 types of vestibular hair cells: react different with afferent dendrite neuron.
One type has calyx.

Question 5

How are the hair cells activated in their different regions? (how is head tilt and linear acceleration detected?)

Answer 5

• The saccule and the utricle detect head tilt and linear acceleration
• Hair cells depolarise, exciting fibres
• Hair cells hyperpolarise, fibres are quiet
• Hair cells are found in a sensory patch called the macula

Question 6

what is the role of the semi-circular canals?

Answer 6

the semi-circular canals detect angular acceleration.

The inertia of endolymph during rotation displaces the cupula.

The semicular canals on either side of the head work in pairs - if we rotate head left fluid moves right.

Question 7

What is the vestal-ocular reflex?

Answer 7

Vestibular nystagmus enables the resetting of eye position during sustained head rotation

• Slow phase: Eyes rotate in the opposite direction to head movement
• Quick phase: Rapid resetting movement back to the centre of the gaze
Right quick phase movement = right beating nystagmus