Hef - Vestibular function

Question 1

semicircular canals

Answer 1

angular/rotational movement

Question 2

saccule and utricle

Answer 2

linear acceleration - translational motion and gravity

Question 3

stereocilia and kinocilium

Answer 3

• resting - cells slightly depolarized releasing small NT
• fluid flow can lead to depolarization (more NT) or hyperpolarization (less NT)
• push toward kinocilium –> K+ influx –> more depolarization and AP –> more glutamate/aspartate release and vice versa
• push away from kinocilium –> close K+ channel –> hyperpolarization –> less NT

Question 4

stimulation of crista ampullaris in semicircular canals

Answer 4

fluid moves cupulla –> move cilia

1. move membranous and bony labyrinth –> fluid stagnant –> stimulate cupulla
2. stop movement –> fluid keeps going –> stimulate cupulla

Question 5

semicircular canal muscles

Answer 5

• horizontal - lateral and medial recti
• LARP - left vertical recti, right oblique
• RALP - right vertical recti, left oblique

Question 6

rotation of head vs. eye movement

Answer 6

• head rotates toward the stimulated vestibular apparatus –> eyes pull in opposite direction to maintain focus
• stimulus from eye is SLOWER than that from vestibule

Question 7

macula

Answer 7

otolith organ in saccule and utricle - contain otoconia

• cilia in both directions –> depolarization both ways
• utricle –> detect horizontal acceleration
• saccule –> detect vertical acceleration and gravity

Question 8

vestibulo-ocular reflex

Answer 8

turn head and eyes remain fixed in opposite direction - maintains focus
-ex. read when moving head

Question 9

vestibulo-collic reflex

Answer 9

head and neck stay on track when body is moving

-ex. chicken

Question 10

vestibulo-spinal reflex

Answer 10

adjust posture when changing positions

Question 11

lateral vestibulospinal tract

Answer 11

IPSILATERAL, maintain posture of lower body/limb

• excitatory signals to ventral horn & muscles
• rigidity (hypertonic) if there is lesion of cerebral cortex –> no inhibitory stimulus

Question 12

medial vestibulospinal tract

Answer 12

mostly ipsilateral, some fibers cross

• keep head posture still in space
• vestibulo-cholic reflex

Question 13

vestibulo-ocular reflex (VOR)

Answer 13

keep eyes still while head rotates

• brain adjusts to eliminate retinal slip
• virtual reality - brain thinks you are moving, but are not

Question 14

optokinetic signal

Answer 14

eye stimulus influences vestibular apparatus

• rotate in dark –> response dies sooner
• rotate in light –> longer response bc have eye stimulation

Question 15

visual vestibular conflict

Answer 15

virtual reality for ex. - brain making you think you have stimulus from vestibular apparatus –> motion sickness
-occurs from vestibular and visual systems being unequal

Question 16

vertigo and nystagmus

Answer 16

vertigo - out of balance; head motion when head is still
nystagmus - associated with tinnitus
-vision stimulus lead to vomiting

Question 17

peripheral vestibular dysfunction

Answer 17

• head tilt, functional imbalance, difficult path integration
• causes: benign positional vertigo (dislodged otoconia), viral, alcohol, menier’s (endolymph pressure), toxins