Balance Flashcards
What is the center of mass (CoM)?
Point at which distribution of mass is equal in all directions
CoM is (dependent/independent) of gravity.
Independent of gravity
T/F CoM changes with body position.
True
Where do you find the CoM on body height? Compared to sacrum?
2/3 of body height above BOS, slightly anterior to sacrum (slightly above belly button)
What is the center of gravity (CoG)?
Vertical projection of CoM
CoG is (dependent/independent) of gravity.
Gravity dependent (take string from top of head down to ankle)
Describe the line of CoG through upright body:
Ankle/knee joints - anterior Hip joint - at or posterior Trunk - midline GH joint - anterior External auditory meatus - through
If you have weakness in legs and can’t support body against gravity, which way will you collapse?
Into direction of gravity
What is base of support (BoS)?
Area beneath a person that includes every point of contact that the person makes with the supporting surface (foot
What is balance?
Control of CoM over BoS
What are 3 aspects of balance?
- Posture control
- Postural stability
- Postural orientation
What is postural control?
control body in space in and out of our base of support
What is postural stability?
control CoM and Cog over BoS in varying sensory environments
ex: tightrope walking
What is postural orientation?
maintain position in space with respect with gravity
What is sensorimotor integration in postural control?
peripheral structures to brain (afferent feedback)
CNS processing is dependent on input from what 3 things?
- Vision
- Vestibular
- Somatosensory
On firm/stable surface what % of:
Somatosensory -
Vestibular -
visual -
Somatosensory - 70%
Vestibular - 20%
visual - 10%
On compliant surface what % of:
Somatosensory -
Vestibular -
visual -
Somatosensory - 10%
Vestibular - 60% (unusual feedback so brain relies on vestibular more)
visual - 30%
As we age, we become more reliant on what input to CNS?
More visually reliant
What input is the dominant sense for upright postural control?
Somatosensory Input - Most active in triggering automatic postural responses in almost all cases
Receptors where will provide information about muscle length, stretch, tension and contraction as well as pressure and joint position?
Receptors (Pressure/light touch, proprioception) located in joints, ligaments, muscles, skin
Central (foveal) vision gives input about what type of oreination?
- Environmental orientation
- Perceptions of vertically and object motion
- Identification of hazards and opportunities
Central (foveal) vision receives (subconscious/conscious) recognition.
Conscious
Peripheral (ambient) vision detects motion of what?
- Detects motion of self in relation to environment
- Head movements, postural sway
Peripheral (ambient) vision receives (subconscious/conscious) recognition.
Subconscious
Visual input assists with what type of postural control in changing environments?
Feedforward (anticipatory) postural control in changing environments
Vestibular input provides what type of information to CNS? Using what structures?
- information to CNS about position and motion of the head
- Semicircular Canals, Otoliths
Vestibular input is unique in its ability to distinguish ___ motion from ___ motion
Unique in its ability to distinguish self-motion from environmental motion
Central sensory structures function first to compare available inputs between ____ and then between ____
between two sides and then between the three sensory systems
Whens changes to the environment occur, what will occur with the sensory systems?
- the relative availability, accuracy, and usefulness of information from the three sensory systems may also change
- Available, accurate, and useful information is “upweighted,” whereas unavailable, inaccurate, or less-useful information is “downweighted.”
Describe changes in sensory input when walking at night:
Vision is down weighted
Somatosensory and vestibular information upweighted
Describe changes in sensory input when walking on beach
Vestibular upweighted
What are the 3 different balance mechanisms?
- Steady state
- Anticipatory postural control
- Reactive postural control
What is steady state balance?
quiet balance – always working on balance but not a lot of work
What is anticipatory postural control?
activating balance in advance based on prior experiences
What is reactive postural responses?
recovery from unplanned perturbation to balance resulting in displacement of CoG or moving the BOS
What is an example of anticipatory postural control?
catching a ball
What type of system and CNS control for anticipatory postural control?
- Feedforward system – relies on prior experience (motor learning/cerebellum)
- Cerebellar control