Lecture 6

Question 1

what is the vestibular system?

Answer 1

balance organs within inner ear that detect acceleration changes

Question 2

Semi circular canals

Answer 2

Detect angular acceleration
- Movement pulls hair cells, triggers increase or decrease in firing rates of cells depending on direction of acceleration

Question 3

Otolith receptors

Answer 3

macular receptors that detect linear acceleration and head orientation with respect to gravity
Saccules and utricles

Question 4

Which way are hair receptors placed in saccules?

Answer 4

laterally

Question 5

Which way are hair receptors placed in utricles?

Answer 5

Vertically

Question 6

Which part of the vestibular system is more important during quiet stance?

Answer 6

Very small angular changes (<1 deg), accelerations primarily linear=otoliths

Question 7

Which part of the vestibular system is more important during dynamic balance?

Answer 7

More angular changes in head orientation=semi-circular canals

Question 8

Increased sway in regards to the vestibular system is seen if…

Answer 8

Acute or compensated vestibular loss
or
tilt head backwards (puts vestibular organs in unusual position. making info unreliable)

Question 9

If a unilateral loss is seen in the vestibular system,

Answer 9

More likely to fall toward side of deficit

Question 10

If a bilateral loss is seen in the vestibular system,

Answer 10

Much greater sway is seen in ALL directions

Question 11

Vestibular illusion

Answer 11

Galvanic stimulation- Pass galvanic current through mastoids
interfere with vestibular signals, changes in orientation
CRANIAL CENTRIC

Question 12

During galvanic stim, to which way does the subject sway

Answer 12

sway toward the side of the anode

Question 13

What is the fukuda test?

Answer 13

Stand with eyes closed, march on the spot
healthy vestibular system can do it
unilateral deficit, rotate toward the side of deficit as postural response

Question 14

Continuous galvanic vestibular stim signal, can stimulate sway behaviour which ___

Answer 14

oscillates with GVS behaviour

Question 15

Proprioceptive signals

Answer 15

• Stretch info from muscle spindles
• tension info from GTO
• Angular info from joint receptors
• Pressure info from cutaneous receptors

Question 16

Evidence for proprioceptive info on balance

Answer 16

increased sway if
- suffer from proprioceptive loss (diabetic)
- Cool feet (remove cutaneous input)
-Ischemic cuff used
-anesthetic
- standing on foam-change
- force transmission used to control sway

Question 17

Haptic cues and balance

Answer 17

• 3 conditions in study
  -no touch info
  -light touch info
  -forceful
• measured COM displacement in tandem stance with eyes open and closed
• Seen drastic decrease in sway in eyes closed condition with no touch vs. light
• similar results seen in cane study conducted by Sozzi et. al., 2017

Question 18

Auditory info on balance, sway decreases if?

Answer 18

• normal hearing with added stationary audio source(white/pink noise)
• Hearing loss is CORRECTED with hearing aids/cochlear implants (relatively weak if all other sources of info still available)

Question 19

Auditory info on balance, sway increases if?

Answer 19

• Normal hearing is suppressed (evidence is weak when all other sensory inputs are available)
• Dynamically changing auditory stimuli (in plane of auditory movement, change position of sound via oscillation)

Question 20

What is redundancy in regards to the CNS

Answer 20

Multiple systems provide parallel info on balance which are integrated together to provide accurate estimates by CNS
- removal of one or two sensory systems does not cause falling!!

Question 21

Unreliability of one sensory system makes removal of other systems _____

Answer 21

more obvious