Balance Flashcards
Center of Mass def and location
Point at which distribution of mass is equal in all directions
Slightly anterior to the sacrum
What is the difference between CoM and CoG
Com is gravity independent
Def and location of CoG
Vertical projection of CoM
Anterior to ankle and knee, posterior to hip, trunk midline, anterior to GH jt, and through external auditory meatus
What is the BOS
Area beneath a person that includes every point of contact that a person makes with the supporting surface
Balance def
Control of com over bos
Postural control v postural stability v postural orientation
Static v dynamic v gravitational demands impacting body position
Balance is the result of CNS processing of what 3 systems
Somatosensory, vestibular, and vision
Sensorimotor input of balance
Mechano and proprioceptors provide info about muscle length, stretch, tensio, and contraction as well as pressure and jt position
Dominant sense for upright postural control (starts at feet)
Visual input for balance is a combination of what 2 types of vision
Central (foveal) vision
Peripheral (ambient) vision
What is the central (foveal) vision responsible for
Environmental orientation
Contributes to perception of verticality and object motion
Identify hazards and opportunities
Which type of vision receives more conscious recognition than peripheral vision
Central/foveal
What is the function of peripheral vision
Detects motion of self in relation to environment (head movements, postural sway)
Largely subconscious
What type of postural control comes from a change in environment
Feedforward/ anticipatory
Vestibular input on balance
Provides information to cns about position and motion of the head via semicircular canals and otoliths (VOR VSR VCR)
How is the vestibular system unique in how it contributes to balance
It can distinguish self motion from environmental motion
CNS processes the available sensory by these receptors in varying degrees by….
Comparing available inputs
Combining inputs
And weighing and redesigning input for all circumstances
When on a firm surface, postural control is achieved from what ratio of sensory input
70 somatosensory
20 vestibular
10 vision
On a compliant surface, postural control is achieved by what ratio of sensory input
60 vestibular
30 visual
10 somatosensory
When changes in the environment occur, the relative ________, _____________, and _________ of information from the sensory systems may also
Availability, accuracy, and usefulness
When reweighing sensory info, available, accurate, and useful info is _________ and unavailable, inaccurate, or less useful info is _________
Unweighted
Downweighted
Any neurological injury to the vestibular, somatosensory, or visual systems will also impact
Balance/ postural stability/control/orientation
Sensory input is processed by cns to allow for descending commands to _______ and ____________ systems to allow for our body to be in one of 3 states…
Motor
Neuromuscular
Steady state, anticipatory control, reactive control
Postural sway
Normal, gentle, and involuntary A&P oscillations
Limits of stability
Points at which CoM approaches the limits of the BOS during postural sway or learning
8º in all directions
Describe Anticipatory postural control
Voluntary, goal-directed movements in preparation for movement
Anticipatory postural control involves motor planning based on ______________ to avoid loss of balance. Making this a ____________system
Past experience
Feedforward
Anticipatory postural control has some _________ control
Cerebellar
What are the most common muscles involved in anticipatory control
UE: bicep
LE: gastroc
Reactive postural control def
Reaction to unplanned perturbations to balance resulting in displacement of CoG or moving the BOS
Reactive postural control is a feedback system dependent on
Fast sensory and motor neurons (heavily myelinated type 1(a) fibers)
What are the 3 reactive strategies and when are they used
Ankle- quiet standing or small perturbations
Hip- large perturbations
Stepping- when other strategies fail
What reactive strategy is the primary strategy for mediolateral control
Hip
What reactive strategy should ultimately increase the BOS
Stepping strategies
Reactive strategies should be ____________ and _________
Automatic and fast
(Sitting/standing) balance has more DOF
Standing 6 deg
Sitting 3 deg
(Sitting/standing) balance is most stable in the A/P position, causing LOB usually laterally
Sitting
Standing is most stable laterally w lob A/P
Anticipatory control in standing balance usually involves what muscles
Gastroc and truck postural muscles
Anticipatory control for sitting balance involves what muscles
Gastroc
Quad
Glute
