Balance Flashcards
where is the COM located in most ppl?
2/3 of body height, above BOS, slightly anterior to sacrum
define balance
control of COM over the BOS
list the 3 primary sensory systems involved in our neurophysiological processing of balance
- Vision
- Somatosensory
- Vestibular
how much of each sensory system is weighed during postural control on a firm/stable surface?
- Somatosensory = 70%
- Vestibular = 20%
- Visual = 10%
how much of each sensory system is weighed during postural control on a compliant surface?
- Vestibular = 60%
- Visual = 30%
- Somatosensory = 10%
what is somatosensory input? How does it impact postural control?
- receptors located in joints, ligaments, muscles, skin provide info about muscle length, stretch, tension and contraction as well as pressure and joint position
- this is the dominant sense for upright postural control
- most active in triggering automatic postural responses
what 2 subtypes of vision make up the visual input aspect of postural control?
- Central (foveal) vision
- Peripheral (ambient) vision
what is central (foveal) vision responsible for?
- environment orientation
- contributes to perceptions of verticality and object motion
- ID of hazards and opportunities
- Recieves more conscious recognition than peripheral vision
what is peripheral (ambient) vision responsible for?
- detects motion of self in relation to the environment
- head movements, postural sway
- largely subconsious
how does visual input impact postural control?
feedforward (anticipatory) postural control in changing environments
T/F: we are more visually reliant when we are younger and become less reliant on vision as we get older and older
FALSE
as we get older we become more visually reliant
how does vestibular input impact postural control?
- provides info to CNS about position and motion of the head
- semicircular canals, otoliths
- VOR, VSR, VCR
- Unique in its ability to distinguish self-motion form environment motion
how does the CNS process all of the inputs from balance senses?
- central sensory structures function first to compare available inputs between 2 sides
- then all 3 sensory systems are compared
- the info is combined to form perceptions of position and motion
*collectively termed multisensory integration/sensory organization
what is multisensory reweighting?
- When changes in the environment occur, the relative availability, accuracy, and usefullness of info from the 3 sensory systems may also change
- Available, accurate, and useful info is “upweighted” whereas unavailable, inaccurate, or less-useful info is “down-weighted”
give an example of multisensory reweighting
walking at night:
- Vision is down-weighted
- Somatosensory and Vestibular info is upweighted
define anticipatory postural control
- Motor planning based on prior experiences to avoid losses of balance
- Voluntary goal-directed movements in preparation for movement
- utilizes feedforward system and cerebellar control
Define Limits of Stability
Points at which COM approaches the limits of the BOS during postural sway or leaning
normal = 8º in all directions
what type of postural sway is normal during sitting? Standing?
- Sitting → around the hip
- Standing → around the ankle
Define reactive postural responses
reaction to unplanned perturbations to balance resulting in displacement of COG or moving the BOS
Feedback system → dependent on fast sensory and motor responses