Lecture 6 Flashcards
what is the vestibular system?
balance organs within inner ear that detect acceleration changes
Semi circular canals
Detect angular acceleration
- Movement pulls hair cells, triggers increase or decrease in firing rates of cells depending on direction of acceleration
Otolith receptors
macular receptors that detect linear acceleration and head orientation with respect to gravity
Saccules and utricles
Which way are hair receptors placed in saccules?
laterally
Which way are hair receptors placed in utricles?
Vertically
Which part of the vestibular system is more important during quiet stance?
Very small angular changes (<1 deg), accelerations primarily linear=otoliths
Which part of the vestibular system is more important during dynamic balance?
More angular changes in head orientation=semi-circular canals
Increased sway in regards to the vestibular system is seen if…
Acute or compensated vestibular loss
or
tilt head backwards (puts vestibular organs in unusual position. making info unreliable)
If a unilateral loss is seen in the vestibular system,
More likely to fall toward side of deficit
If a bilateral loss is seen in the vestibular system,
Much greater sway is seen in ALL directions
Vestibular illusion
Galvanic stimulation- Pass galvanic current through mastoids
interfere with vestibular signals, changes in orientation
CRANIAL CENTRIC
During galvanic stim, to which way does the subject sway
sway toward the side of the anode
What is the fukuda test?
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
Continuous galvanic vestibular stim signal, can stimulate sway behaviour which ___
oscillates with GVS behaviour
Proprioceptive signals
- Stretch info from muscle spindles
- tension info from GTO
- Angular info from joint receptors
- Pressure info from cutaneous receptors
Evidence for proprioceptive info on balance
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
Haptic cues and balance
- 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
Auditory info on balance, sway decreases if?
- 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)
Auditory info on balance, sway increases if?
- 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)
What is redundancy in regards to the CNS
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!!
Unreliability of one sensory system makes removal of other systems _____
more obvious
