Lec 10 Vestibular

Question 1

Otolith organs respond to ____ movements

Answer 1

linear acceleration

Question 2

Semicircular Canals respond to ____ movements

Answer 2

rotational accelerations

Question 3

Utricle = what plane?

Answer 3

horizontal (L/R)

Question 4

Saccula = what plane?

Answer 4

Vertical (up/down)

Sagittal (front/back)

Question 5

Anatomy of the otolith organs

Answer 5

Macula = sensory epithelium.
Hair cells on macula.
Otolithic membrane (gelatinous layer) = on top of hair cells.
Otoconia (crystals) = in membrane.

Question 6

Purpose of Otoconia?

Answer 6

Adds weight to membrane; when head moves, creates a shearing motion btwn membrane & macula.

Question 7

Ampulla - located where? Cell types?

Answer 7

base of each of the 3 canals.

crista (supporting cells) + hair cells.

Question 8

Capula - what is it

Answer 8

bundle of hair cells in ampulla projecting into gelatinous mass; surrounded by endolympth.

Question 9

Capula moves in the ____ direction as head movement

Answer 9

opposite

Question 10

When Hair Cells depolarize, they increase activity in CN __

Answer 10

8

Question 11

Semicircular canal on ipsilateral side (to head turn): increase or decrease APs?

Answer 11

increase

Question 12

Semicircular canal on contralateral side (to head turn): increase or decrease APs?

Answer 12

decrease

Question 13

Distal processes of CN 8

Answer 13

invx semi canals & otolith

Question 14

Central processes of CN 8

Answer 14

project to vestibular nuclei (in brainstem)

Question 15

Vestibular Nuclei projects to… (4)

Answer 15

CN 3/4/6 (eye movement)
Spinal Cord
Thalamus
Cerebellum

Question 16

Vestibular Nuclei project to CN 3/4/6 via ____

Answer 16

MLF

Question 17

Vestibulospinal purpose

Answer 17

postural adjustments

Question 18

VOR Pathway for head turning Left

Answer 18

Medial Vestibular Nucleus sends:

1. Excitatory to Right Abducens (R lat rectus contracts)
2. Inhibitory to Left Abducens (L lat rectus relax)
3. Inhibitory to Right Oculomotor (R med rectus relax).

Right Abducens projects to Left Oculomotor (L med rectus contracts).

Question 19

Physiological Nystagmus

Answer 19

due to net difference in AP firing rates btwn R/L semicircular canals.
Slow movement = opposite to head movement.
Fast movement = towards direction of head.

Question 20

Pathological Nystagmus

Answer 20

due to unilateral damage.
CNS always thinks head moving to one direction.
Nodding eye movements w/o head motion.

Question 21

Cold water mimics head movement ____ irrigated ear (away from/towards)

Answer 21

away from

Question 22

Warm water mimics head movement ____ irrigated ear (away from/towards)

Answer 22

towards

Question 23

Eye movements with cold water

Answer 23

slow towards.

fast away.

Question 24

Eye movements with warm water

Answer 24

slow away.

fast towards.