Lecture 12 9/8/23

Question 1

What are the two functions of the vestibular system?

Answer 1

-maintain upright posture
-coordinate head movement with eye movement

Question 2

How do the eyes move in relation to head movement?

Answer 2

when the head moves, the eyes will move in the opposite direction in order to maintain a steady image

Question 3

Where are the sensory organs of the vestibular system?

Answer 3

inner ear

Question 4

What parts of the inner ear are important for the vestibular system?

Answer 4

-utricle and saccule
-3 semicircular canals

Question 5

What do the utricle and saccule sense?

Answer 5

linear acceleration and gravity

Question 6

What do the semicircular canals detect?

Answer 6

rotary acceleration

Question 7

How do the hair cells of the vestibular system work?

Answer 7

-the cells are tonically active
-bending one way increases activity
-bending another way decreases activity

Question 8

What is important about the way the semicircular canals are arranged?

Answer 8

-one is in each dimension
-can detect movement in all three planes

Question 9

Why are the cilia able to detect movement?

Answer 9

fluid lags with movement and will flow over the cilia, causing them to bend

Question 10

What is the cupula?

Answer 10

a jelly-like substance over the hair cells that bends around them

Question 11

What are the utricle and saccule?

Answer 11

ridges filled with hair cells

Question 12

Why are the otoliths on the on the surface of the cupula important?

Answer 12

they provide weight to help bend the hair cells

Question 13

What are the two paths of the vestibular system?

Answer 13

-path rostrally that makes the eyes move
-path to the spinal cord and LMNs to maintain posture

Question 14

What is the role of the vestibular nuclei?

Answer 14

take inner ear input and compare the two to detect rotation and gravity

Question 15

What happens when the head is level and not rotating?

Answer 15

there is equal electrical activity and exert equal extensor muscle messages

Question 16

What happens when the head leans to the left?

Answer 16

-greater elec. activity on the left
-more extensor messages and muscle activity on left side

Question 17

What happens when there is a lesion on the left inner ear?

Answer 17

-there is no elec. activity on the left, only the right
-extensor muscle signals only on right side
-patient leans left towards lesion

Question 18

What are the rotation-induced eye movement?

Answer 18

-eyes move in an equal and opposite direction
-forebrain induces corrective movement towards direction

Question 19

How do the eyes move when there is a lesion on the left inner ear?

Answer 19

-eyes move to the left towards lesion
-corrective phase to the right, away from lesion

Question 20

What is spontaneous nystagmus?

Answer 20

-eyes drift towards lesion
-quickly correct away from lesion
-eyes move when patient is not rotating

Question 21

What is pendular nystagmus?

Answer 21

-eyes moving equal speed in each direction
-congenital abnormality
-NOT vestibular

Question 22

What is the role of the cerebellum?

Answer 22

inhibit the vestibular nuclei

Question 23

What happens when there is a left cerebellar lesion?

Answer 23

-left vestibular has no inhibition
-increased activity and extensor tone on left side
-animal leans to the right side, away from lesion

Question 24

What occurs in bilateral vestibular disease?

Answer 24

-animal will stay in a crouched position
-head will dramatically move from side to side

Question 25

Would animals with bilateral vestibular disease have physiologic nystagmus?

Answer 25

no, because their brain cannot sense if they are rotating