Week 3 Flashcards
What is postural control?
Involves controlling the body’s
position in space for stability and orientation
What is postural orientation?
Ability to maintain appropriate
relationship between body segments and between body and environment for a task
What is postural stability?
Ability to control the center of mass (COM) in relationship to the base of support (BOS)
What is Center of Mass (COM)?
Point at center of total body mass, determined by finding weighted average of the COM of each body segment
What is Center of Gravity (COG)?
Vertical projection of COM
What is Base of Support (BOS)?
Area of body that is in contact with support surface
What is center of Pressure?
Center of the distribution of the total force applied to the supporting surface. COP moves continuously around the COM to keep COM within support base
All tasks require __
All tasks require postural control
Every task has an ___ component and a ___
component
Every task has an orientation component and a stability
component, and each varies with the task and the environment
The relationship between orientation and stability is ____
Inverse
What does postural control emerge from?
An interaction of the individual, the task with its inherent postural demands, and the environmental constraints postural actions
What are the components of balance?
- Postural tasks
- Individual
- Environment
What are the motor components of posture and the individual?
Musculoskeletal, muscle synergies
What are the sensory components of posture and the individual?
Sensory systems, sensory organization
What are the cognitive components of posture and the individual?
Cognitive strategies, cognitive resources (cognitive doesn’t necessarily mean conscious control)
What is included in the cognitive components of posture and the individual?
Attention, motivation, intent; also ability to adapt in response to changing demands, anticipatory aspects of postural control based on previous experience and learning
What is the relationship between task being handled at once and attention available for posturing and balance?
Inverse, the more task being being handled at once, the less attention available for posturing and balance
What are the support surfaces components of posture and the environment?
Changing support surfaces affects organization of muscles and forces needed to balance
What are the sensory context components of posture and the environment?
Differences in visual and surface conditions affect way sensory info used for balance
What are the cognitive load components of posture and the environment?
Multi tasking affects the way things like attention are used for balance
What may the attention required for postural task lead to?
May reduce performance of second task
What is the definition of postural task: steady state?
Ability to control COM relative to BOS in fairly predictable, stable and non-changing conditions
What is the definition of postural task: proactive?
Ability to activate muscles in legs and trunk for balance control in advance of potentially destabilizing voluntary movements. Relies on feed forward condition (anticipatory posture for destabilization)
What is the definition of postural task: reactive?
Ability to recover a stable position following an unexpected perturbation. Relies on feed back mechanism
What are the contributions to postural control?
- Body alignment
- Muscle tone
- Postural tone
How does body alignment contribute to postural control?
Minimizes effect of gravitational forces
How does muscle tone contribute to postural control?
Keeps body from collapsing in response to pull of gravity
How does postural tone contribute to postural control?
Keeps body from collapsing in
response to pull of gravity. The activation of the anti-gravity muscle
Where is fixed support recovery of balance?
- Ankle
* Hip
When is ankle strategy used?
In small perturbations. Requires good ROM of the ankle
When is hip strategy used?
When the perturbation is larger and or faster, and when the BoS is concurrent or smaller than the feet
When is the change in support recovery of balance used?
When there is a change in BoS
What is the stepping strategy?
Re- aligning the BoS under a falling CoM. Always preceded by a medio-lateral anticipatory postural adjustment. Before you can take a quick step, there has to be a shift in CoM in one direction or the other
Who are those that will find the stepping strategy very difficult to accomplish?
Patients with decreased ability to weight shift over their BoS. (stroke or weakness due to injury. will do for reach-to-grasp instead)
How does the reach-to-grasp strategy work?
By extending the BoS by using the arm
____ makes it possible to ensure that the forces generated from one point doesn’t produce instability in the other parts of the body
CNS makes it possible to ensure that the forces generated from one point doesn’t produce instability in the other parts of the body
What do postural muscles activated before voluntary
movements do?
Minimizes disturbance to balance
What do visual, somatosensory, and vestibular systems that provide info about body position and movement in space with respect to gravity and environment do?
Each provide different frame of reference for postural control
What are the spinal contributions to controlling postural orientation and stability?
Tonically active extensor muscles for antigravity support in postural orientation; somatosensory contributions to postural control
What are the brainstem contributions to controlling postural orientation and stability?
Level of postural tone, automatic postural synergies that occur during poor posture, vestibular contributions to postural control
What are the basal ganglia contributions to controlling postural orientation and stability?
Postural Set (ability to quickly change muscle patterns)
What are the cerebellum contributions to controlling postural orientation and stability?
Control of adaptation (ability to modify postural muscle amplitude)
What are the consequences of impaired stability?
- Loss of functional independence
- Reduced or restricted participation
- Reduced confidence
- Increased fall risk
What are the characteristics of alignment as a problem in motor systems?
Often changed in persons with neuromuscular dysfunction
What are the characteristics of postural sway as a problem in motor systems?
Increased postural sway area and velocity; asymmetrical sway area. Sway areas will be biased towards the active area
What are the characteristics of functional stability limits as a problem in motor systems?
Reduced limits of stability
(reduced COP excursion). Inability to move CoP over the BoS, causes instability
What are the characteristics of steady-state balance in sitting as a problem in motor systems?
All about control of trunk
segmentally; good prognostic indictor of outcome following stroke and TBI.
What are the components of impaired reactive balance?
- Sequencing Problems
- Coactivation
- Delayed onset of postural responses
- Problems modifying postural strategies
- Impaired central set
What are sequencing problems?
The inability to sequence firing muscle. Simply messes with the sequence with which the needed muscles are activated
What is central set?
The ability to adapt quickly to changes in task and or the environment. Gets impaired due to neurological injuries
What are the components of impaired change in support strategies?
- Lack of anticipatory lateral weight shift
- Delayed onset of support strategy
- Take many steps to recover
When is anticipatory lateral weight shift critical?
Before any stepping strategy can occur.
What are the components of impaired anticipatory postural control?
• Heavily dependent on previous experience and
learning
• Lack of anticipatory activation in “affected side” in stroke, brain injury
• Lack of anticipatory trunk activation
• Seen with lesions in many areas of nervous system
- Circuitry for anticipatory postural control involves
supplementary motor cortex, basal ganglia, and cerebellum
What are the characteristics of sensory problems that can affect reactive balance?
- Triggers centrally organized postural synergies
- Providing direct sensory feedback to scale magnitude of automatic postural responses. This ensures that the sensory response given is proportionate to the instability/imbalance felt
What are the characteristics of sensory problems that can affect anticipatory balance?
- Profound changes in motor adaption
* Earlier activation of anticipatory postural adjustments (compensation)
What are the characteristics of perceptual problems that can affect postural control?
• Perceptions of verticality: often impaired in stroke,
correlates with poor balance
What are the characteristics of balance and falls self-efficacy as a problem in cognitive systems?
- Confidence in ability to perform activities without losing balance or falling
- Lack of self-efficacy is common in persons with neuromuscular dysfunctions
What are the characteristics of impaired postural stability and dual-task interference as a problem in cognitive systems?
- Amount of attention required depends on difficulty
- Impaired postural control increases attentional demands of balance
- Less reserve for other tasks
What is agnosia?
An inability to recognize or perceive familiar sensory information even though the sensory system is without deficit.
Disturbance of one of the sensory modes of visual,
tactile, proprioceptive, and auditory, or may involve
problems in body scheme
What is visual agnosia?
• Perception without meaning, inability to recognize visual stimuli despite adequate visual functioning • Failure to recognize familiar colors, objects or name them using vision
What is prosopagnosia?
Failure to recognize people or faces. Highly uncommon
How is the evaluation of agnosia done?
• Rule out sensory deficit and
anomia
• Object recognition
• Visual Identification of Objects