Vestibular reflexes

Question 1

what is the vestibular ocular reflex (VOR)

Answer 1

stabilises the eyes in space when the head is moved around
- head rotates and the eyes counter rotate to stay fixed in position

Question 2

where does the info for the VOR come from

Answer 2

SC canals

Question 3

what causes horizontal VOR

Answer 3

rotating head left and right
- horizontal SC canals

Question 4

what causes vertical VOR

Answer 4

tilting head fwd and bwd
- combo of anterior and posterior SC canals

Question 5

what causes torsional VOR

Answer 5

rolling head side to side
- combo of anterior and posterior SC canals

Question 6

what is the muscular response in a VOR when the head turns to the left

Answer 6

(horizontal VOR)
activates vestibular afferents on the left
- right lateral rectus and left medial rectus = increase firing
- left lateral rectus and right medial rectus = decrease firing

Question 7

what is the wiring of the VOR (when head turns to the left)

Answer 7

starts in SC canals
- neurons come into scarpa’s ganglion and synapse onto one inhibitory and one excitatory neuron
- inhibitory neuron travels ipsilaterally
— synapses onto left lateral and right medial
- excitatory neuron travels contralaterally
— synapses onto right lateral and left medial

Question 8

what is the vestibulo collic reflex (VCR)

Answer 8

stabilises the head in space when moving around
- head is tilted and the neck counter rotates to keep the head in a fixed position (working against gravity)

Question 9

what causes coronal VCR

Answer 9

tilting head side to side

Question 10

where does the info for the VCR come from

Answer 10

info comes from tilt
- utricle and saccule

Question 11

what occurs during coronal VCR when the head is tilted to the left

Answer 11

• increased firing in medial porton of left utricle and lateral portion of right utricle
• decreased firing in lateral portion of right utricle and medial portion of right utricle

Question 12

what is the muscular reaction to VCR when head is tilted to the left

Answer 12

increased contraction of the lateral flexor MNs on the right side of the head
(head wants to be vertical)

Question 13

which flexors do lateral portions of utricles connect to

Answer 13

ipsilateral flexors
(same side)

Question 14

which flexors do medial portions of utricles connect to

Answer 14

contralateral flexors
(opposite side)

Question 15

what are vestibular spinal reflexes

Answer 15

vestibular reflexes that control posture and balance