Motor Control Postural Control Quiz
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114 Terms
What is postural orientation?
Maintaining an appropriate relationship between the body and surroundings
What is postural stability?
Controlling the center of mass relative to the base of support
What is the base of support (BOS)?
Area including all contact points with the supporting surface
What is center of mass (COM)?
Point representing the mean position of matter in the body
What is the vertical projection of COM?
Point on the support surface directly below the COM
What is center of pressure (COP)?
Location of the vertical ground reaction force vector
What happens when COP and COM are not aligned?
A torque is applied that causes the body to tilt
What happens when the vertical projection of COM is outside the BOS?
The system becomes unstable
What are limits of stability (LOS)?
Maximum distance a person can sway or lean without changing BOS
What clinical test can assess limits of stability?
Functional Reach Test
What instrument can measure COP displacement?
Force plate
How does reducing BOS generally affect balance difficulty?
It makes postural control more challenging
What are the three main sensory systems for balance?
Vision and somatosensation and vestibular
What does allocentric sensation describe?
Body position relative to other objects
Which sensory system provides allocentric information?
Vision
What does egocentric sensation describe?
Body position relative to itself
Which sensory system provides egocentric information?
Somatosensory or proprioceptive system
What receptors contribute to proprioception?
Muscle spindles and Golgi tendon organs and skin receptors
What does geocentric sensation describe?
Body acceleration and position relative to gravity
Which sensory system provides geocentric information?
Vestibular system
Which vestibular structures detect angular acceleration?
Semicircular canals
Which vestibular structures detect linear acceleration?
Utricle and saccule
Which sensory system often resolves conflicting sensory information?
Vestibular system
What is sensory integration?
Combining sensory inputs in the brain for postural control
What is sensory reweighting?
Rapidly adjusting reliance on sensory signals according to reliability
When is sensory reweighting particularly important?
When sensory information becomes inaccurate or conflicting
On a firm surface what percentage of balance input is somatosensory in the handout?
70%
On a firm surface what percentage of balance input is vestibular in the handout?
20%
On a firm surface what percentage of balance input is visual in the handout?
10%
On an unstable surface what percentage of balance input is somatosensory in the handout?
60%
On an unstable surface what percentage of balance input is vestibular in the handout?
30%
On an unstable surface what percentage of balance input is visual in the handout?
10%
What does the Sensory Organization Test (SOT) assess?
Balance under different sensory conditions
What is quiet stance?
Standing while making ongoing small postural adjustments
What are three postural strategies discussed in the handout?
Ankle and hip and stepping strategies
What is reactive postural control?
Rapid balance responses after an unexpected perturbation
What is another name for reactive postural responses?
Automatic postural responses (APRs)
When do reactive responses occur relative to a perturbation?
After the perturbation
How quickly does reactive muscle activity begin in healthy controls?
Approximately 90 milliseconds
Are reactive postural responses faster than voluntary steps?
Yes
Are reactive postural responses faster than spinal reflexes?
No
What does context specificity mean in reactive balance?
The response changes based on environment and challenge and arousal
What brain region helps switch reactive responses across contexts?
Basal ganglia
What brain region helps adapt responses based on prior experience?
Cerebellum
What intervention can improve reactive stepping?
Perturbation training
What is an anticipatory postural adjustment (APA)?
A postural response that precedes an expected or voluntary movement
Are APAs feedforward or feedback control?
Feedforward control
How can stronger APAs influence later corrective responses?
They can reduce the need for compensatory reactions
Can APAs improve with training?
Early evidence suggests yes
What brain region integrates environmental information during postural responses?
Cortex
What brain region contributes heavily to postural responses?
Brainstem
Which requires more cortical involvement: stepping or an in-place response?
Stepping
What happens to muscle power with normal aging?
It generally decreases
How can aging affect joint range of motion?
Increased stiffness and reduced flexibility
How does aging affect the three sensory systems?
Vision and proprioception and vestibular function generally decline
Which sensory system often receives greater weighting with aging?
Vision
How does quiet stance sway generally change with aging?
It increases
How do limits of stability change with aging?
They decrease
How do APAs typically change with aging?
They become later and smaller
How do automatic postural responses change with aging?
They become slower and show more coactivation
Are reactive muscle synergies usually preserved in healthy aging?
Yes
What is a muscle synergy?
A group of muscles activated together as a motor program
What happens to attention demands during challenging balance tasks?
They increase
How does a dual task affect older adults during challenging standing?
Secondary task reaction time becomes more delayed
How can fear of falling worsen balance?
It reduces confidence and participation and can contribute to instability
What percentage of adults over 65 fall each year according to the handout?
About 30%
What lateral stepping pattern is more common in older adults after loss of balance?
Taking an additional lateral step
What risk is associated with crossover stepping during lateral balance loss?
Limb collisions and falls
What can repeated perturbations improve in older adults?
Reactive stepping
How does Parkinson disease affect APA size and timing?
APAs are smaller and delayed
How does Parkinson disease affect reactive step size?
Steps are smaller
What is the characteristic reactive response flexibility deficit in Parkinson disease?
Difficulty switching responses across contexts
How is reactive response latency classified in Parkinson disease in the summary table?
Within functional limits
How is reactive response adaptability classified in Parkinson disease in the summary table?
Within functional limits
Why may quiet stance sway be unusually low in some people with Parkinson disease?
Rigidity
What contributes to reduced stability limits in Parkinson disease?
Stooped posture and rigidity
Why are crossover steps especially risky in Parkinson disease?
More limb collisions and falls
What is the characteristic reactive response deficit in multiple sclerosis?
Delayed onset of postural responses
What causes delayed postural responses in MS according to the handout?
Distorted and slowed conduction of afferent signals
How is reactive response size classified in MS in the summary table?
Within functional limits
How is reactive response flexibility classified in MS in the summary table?
Within functional limits
How is reactive response adaptability classified in MS in the summary table?
Within functional limits
What is a characteristic postural response in cerebellar dysfunction?
Large hypermetric responses
How does cerebellar dysfunction affect adaptation to prior perturbations?
Adaptability is impaired
How is reactive response latency classified in cerebellar dysfunction in the summary table?
Within functional limits
How is reactive response flexibility classified in cerebellar dysfunction in the summary table?
Within functional limits
Which disorder has small but adaptable reactive responses?
Parkinson disease
Which disorder has large and poorly adaptable postural responses?
Cerebellar dysfunction
Which disorder is particularly associated with delayed reactive responses?
Multiple sclerosis
T or F: Postural stability involves controlling COM relative to BOS
True
T or F: COP and COM are identical concepts
False
T or F: A walker can increase the base of support
True
T or F: Limits of stability require taking a step
False
T or F: Vision provides allocentric sensory information
True
T or F: The semicircular canals detect linear acceleration
False
T or F: Vestibular input becomes more important on an unstable surface in the handout example
True
T or F: Sensory weighting should remain constant when sensory information becomes unreliable
False
T or F: Quiet standing involves ongoing postural control
True
T or F: Reactive postural responses occur before a predictable voluntary movement
False
T or F: Reactive postural responses can change with practice
True