Vestibular System

Question 1

What is the function of the vestibular system?

Answer 1

Movement and position of the head relative to gravity.

Question 2

Where are the receptors of the vestibular system located?

Answer 2

Vestibular Labrynth.

Question 3

How many types of receptors does the vestibular system have?

Answer 3

One type.

Question 4

What type of receptor is the vestibular system made up of?

Answer 4

Hair cells.

Question 5

What are hair cells attached to?

Answer 5

• Primary afferent neurons.
• These primary afferent neurons form the 8th cranial nerve, known as the vestibular cochlear nerve.

Question 6

What do the primary afferent neurons of the vestibular system attach to?

Answer 6

• Synapse with interneurons + LMN’s.
• For the functioning of the visual ocular reflex cycle.

Question 7

What is the vestibular labyrinth?

Answer 7

Sub structure within the ear that contains all the receptors.

Question 8

What are the 5 subdivisions of the vestibular system?

Answer 8

• 3 pre-semicircular canals:
  1. Anterior.
  2. Posterior.
  3. Horizontal.
• 2 otolith organs:
  1. Utricle.
  2. Saccule.

Question 9

What is the function of the pre-semicircular canals?

Answer 9

Respond to angular acceleration and deceleration.

Question 10

What is the function of the overall otolith organs?

Answer 10

Respond to linear acceleration and deceleration.

Question 11

What is the function of the utricle organ?

Answer 11

Detects movement in the horizontal plane.

Question 12

What is the function of the saccule?

Answer 12

Detects movement in the sagittal plane.

Question 13

What are the subdivisions of the vestibular labyrinth made up of?

Answer 13

Endolymph.

Question 14

What are the hair cells embedded in within the vestibular labyrinth?

Answer 14

Gel like substance.

Question 15

What are the differences between maculae and cristae?

Answer 15

• Maculae have hair cells with crystals on top.
• Crista does not have hair cells or crystals.

Question 16

Describe how hair cells function in the vestibular labyrinth.

Answer 16

• Movement of endolymph within the labyrinth moves the gel and hair within it.
• The movement of hair is the stimulus for an action potential along the primary afferent neuron it is attached.

Question 17

Outline the step by step process on how nerve impulses travel within the vestibular system.

Answer 17

1. Primary afferent neurons originate as a hair cell in the vestibular labrynth.
2. Cell bodies of these neurons are located in the vestibular ganglion.
3. Axons of these primary afferent neurons travel via the vestibular cochlea nerve and terminate in the vestibular nuclei in the brainstem.
4. Vestibular nuclei are located in the medulla of the brainstem.
5. Other neurons that do not terminate in the vestibular nuclei travel directly to the cerebellum.
6. Secondary afferent neurons cell bodies are located in the brainstem.
7. These neurons ascend and terminate in the thalamus.
8. Secondary afferent neurons will synpase with tertitary afferent neurons.
9. Teritiary afferent neurons transmit information to the insular lobe.

Question 18

What is the insular lobe?

Answer 18

• Located deep in the lateral sulcus.
• Made up of the frontal, parietal and temporal lobes.

Question 19

Describe the functioning process of the vestibular system.

Answer 19

• There will be movement of endolymph fluid in the semicircular canals.
• The fluid will move towards the hair cells on one side.
• On the other side fluid moves away from the hair cells.
• This increases the firing rate, therefore leading to more action potentials on one side (side where there is more fluid).
• The side where there is less fluid inhibits a decrease in firing rate.
• The difference in firing rate on each side commincates to the brain where the head has moved.