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47 Cards in this Set

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List the 2 frameworks in rehabilitation science for posture and balance
1. reflex/hierarchical theory
2. systems theory
The postural control system is an integrated system of
musculoskeletal and neural systems
Define the reflex/heirarchial theory of posture/balance
- there is an organization of reflex responces from independent sensory systems
- these transition from initial spinal reflexes to higher cortical responses with age
Define the systems theory of posture/balance
postural control is an interaction of 3 key things:
- individual
- task
- environment
and the sucessful responce depends on an integrated neuromusculoskeletal system
What are the two purposes of postural contol?
1. stability
2. orientation
Define postural control
controlling the body's position in space for the dual purposes of stability and orientation
Define postural orientation
ability to maintain an apropriate relationship between (1) the body segments and (2) the body and the environment
3 keys sensory systems for general postural control in functional tasks
- vestibular (gravity)
- somatosensory (support surface)
- visual (relation to objects in environment)
General body position in most functional tasks
vertical (importance of gravity)
Define postural stability
- balance
- ability to maintain the body in equilibrium
List the two types of postural stability
- statis (at rest)
- dynamic (in motion)
Describe postural stability in the sense of steady state
stable system is one whose movement is not significantly altered from a desired trajectory even when it is given perturbations.
Most basic stable body configuration
center of mass is maintained over base of support
How is center of mass determined
the weighted average of the center of mass of each body segment
What do we call the vertical projection of the center of mass?
center of gravity
Define center of gravity
the vertical projection of the center of mass
Define postural stability in terms of center of mass
the abiity to mainatin the center of mass within the limits of the base of support
In balance, the base of support is also called
stability limits
Factors affecting dynamic state of stability limits
- task
- individual biomecanics
- environment
Define the center of pressure
The vertical projection of the muscular forces acting on the center of mass
What do we call the vertical projection of the muscular forces acting on the center of mass?
the center of pressure
7 conceptual systems contributing to postural control
1. musculoskeletal
2. internal representations
3. adaptive mechanisms
4. anticipatory mechanisms
5. sensory strategies
6. indivual sensory systems
7. neuromuscular synergies
Describe perception and action in postural control
need to be able to (1) integrate sensory information to assess the position and motion of the body in space and (2) generate forces for controlling body position systems.
Define adaptive postural control
modifying sensory and motor systems in response to changing task and environmental demands
"other" aspects of cognition that affect postural control
- attention
- motivation
- intent
Define postural motor strategies
organization of movements appropriate for controlling the body's position in space
When standing what is the primary direction of sway?
forward/backward
What three factors contribute to our background muscle tone during quiet stance?
1. intrinsic stiffness of muscles themselves
2. background muscle tone
3. postural tone (activation of antigravity muscles)
2 general categories of factors that contribute to stability in quiet stance
1. alignment
2. muscle tone
Through what points does the vertical line of gravity fall if there is good alignment during quiet stance?
- mastoid
- anterior to shoulder
- at or just post to hip
- anterior to knee
- anterior to ankle
List the muscles that are tonically active during the control of quiet stance
- erector spinae
- iliopsoas
- gluteus medius
- gastrocnemius
- tensor fascia latae
- soleus
- abdominals (intermittent)
- tibialis anterior (with backwards sway)
- biceps femoris
Define muscle tone
the force with which a muscle resists being lengthened (its stiffness)
General thoughts about cause of resting muscle tone
- caused by low levels of free calcium in muscle fiber
- cause low level of continual recycling of cross-bridges
- considered a non-neural mecahnism
Important reflexes in postural tone
- tonic neck reflex
- vestibulocollic reflex
- vestibulospinal reflex
Center of pressure (COP) mobility in person's with Parkinson's
decreased
Center of pressure (COP) mobility in dancers
increased
In general, describe the relationship between center of pressure mobility and postural control
Generally more mobility (more sway) reflects less control
General range of limits of stability in stance
- A/P limits: 50-80% of foot length
- Med/lat limits: 60-80% of stance width
Describe a synergy in postural control
the functional coupling of groups of muscles such that they are considered to act together as a unit
List the 3 major strategies for anterior posterior stability in quiet stance
1. ankle strategy
2. hip strategy
3. stepping strategy
When is the ankle movement strategy typically used and what must be intact?
- usually in situations where the perturbation is small and the support surface is firm
- need intact ROM at ankles and good muscle strength
Describe the ankle movement strategy to correct for forward sway
gastrocnemius, then hamstrings, then paraspinals
Describe the ankle movement strategy to correct for backward sway
anterior tibialis, then quadriceps then abdominal muscles
In general what is the progression of muscle contraction in the ankle movement strategy?
muscles activate in order from distal to proximal
General description of the hip strategy for controlling body sway
produces large and rapid motion at the hip joints with antiphase rotation of the ankles
Typical situations in which the hip strategy is used for controlling body sway
- faster, larger perturbations
- support surface is complicated or smaller than the feet (like a beam)
When is the stepping strategy used for controlling body sway?
when in-place strategies (such as ankle and hip) fail