Vestibular system

Question 1

Explain how angular acceleration is detected in the semicircular canals

Answer 1

With head movement, endolymph moves in the ampulla (swelling at end of semicircular canal) and hits the cupula - hair cells sit under the cupula and get bent with cupula movement - bending of hair cells causes firing of primary vestibular neurons

Question 2

What are the two otolith organs? What is their function?

Answer 2

Utricle and saccule

Detect head movement and linear acceleration

Question 3

How do the otolith organs differ from the ampulla in detecting movement (what are the structural differences?)

Answer 3

Still have hair cells, but no cupula, instead it is an otolithic membrane filled with calcium carbonate crystals that sits on top of the hair cells

Question 4

What kind (structural) of neurons are the primary vestibular neurons?

Answer 4

Bipolar

Question 5

How does the vestibulo-ocular reflex work?

Answer 5

Eyes move equal and opposite to head movement

Requires connection between the vestibular nuclei and ocular muscles via the medial longitudinal fasciculus

Question 6

When does nystagmus occur normally?

Describe what nystagmus looks like

Answer 6

During sustained rotation

Slow phase (toward movement) followed by rapid phase (away from movement)

Question 7

How is nystagmus named?

How does the direction of the nystagmus relate to the side of the lesion?

Where does a lesion occur for nystagmus to happen?

Answer 7

According to the direction of the rapid phase

Quick phase is away from the lesion

Lesions in vestibular system can cause nystagmus

Question 8

What is Meniere’s disease caused by?

Answer 8

Excess endolymph