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S2 Movement Science > Motor Control III > Flashcards

Motor Control III Flashcards

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1
Q

postural control

  • definition
  • purposes
A

controlling the body’s position in space with dual purpose of

  • orientation
  • stability (postural equilibrium)
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2
Q

postural control: orientation

-what is it

A

ability to maintain an appropriate relationship between body segments and between the body and environment

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3
Q

postural control: stability

  • what is it
  • commonly referred to as…
A

ability to maintain one’s center of mass within the limits of the base of support
commonly referred to as “balance”

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4
Q

stability and orientation requirements vary with…

A

task and environment

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5
Q

primary goals of nervous system in postural control

A

control position and motion of the body’s COM

body’s rotation about the COM

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6
Q

COM

  • define
  • location in humans
  • what is center of gravity
A

point that represents the average position of the body’s total mass
located 20 mm anterior to S2 in erect stance; instantaneous location depends on body position
COG
-vertical projection of COM onto support surface

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7
Q

BOS definition

A

area of the body that is in contact with the support surface

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8
Q

limits of stability (LOS)

-what is it

A

maximum range COM can be moves without changing BOS

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9
Q

center of pressure (COP)

-what is it

A

center of distribution of total force applied to support surface

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10
Q

for body to be in static equilibrium…

A

COP and COM must align over BOS

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11
Q

how is COM restored to desired position

A

torque created by action of trunk and limb muscles

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12
Q

COM and COP illustration

A 
COM = sheep
COP = sheepdog
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13
Q

current view of motor control of posture

A

complex motor skill derived from interaction of multiple sensorimotor processes and systems

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14
Q

systems framework for postural control

-components

A 
individual
-motor, sensory, cognitive
postural task
-steady state, proactive, reactive
environment
-support surface, sensory context, cognitive load
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15
Q

individual systems/constraints

A 
motor
-musculoskeletal
--strength, ROM, alignment
-neuromuscular
--postural tone, amplitude, timing
sensory
-visual, vestibular, somatosensory
cognitive
-attention, adaptation, anticipation, confidence
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16
Q

task constraints

-functional tasks require what 3 types of postural control

A

steady state
reactive
proactive

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17
Q

steady state control

  • what does it do
  • when
A

control COM relative to BOS in predictable, non-changing conditions

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18
Q

reactive control

-what is it

A

recover a stable position after an unexpected pertubation

19
Q

proactive control

-what is it

A

activation of muscles in advance of potentially destabilizing voluntary movements to avoid instability

20
Q

feedback control (closed-loop)

  • used in response to…
  • example
A

used in response to external disturbances to equilibrium

during gait and in response to disruptions of gait (trip.slip)

21
Q

feed-forward control (open-loop)

-what is it

A

pre-planned synergistic movements in anticipation of a voluntary movement

22
Q

central command for a voluntary limb movement is associated with…

A

a simultaneous feed-forward command anticipating an expected postural pertubation

23
Q

voluntary movement can perturb postural equilibrium, but knowledge of these potential pertubation is built into…

A

the voluntary motor commands and used to offset their adverse effects ahead of the event by feed-forward motor action

24
Q

anticipatory actions must be _____, but eventually they _____

A

must be learned, but eventually they operate automay

tically in an open loop manner, being triggered by specific intended movements

25
Q 
steady state (static) balance
-factors
A

musculoskeletal alignment
muscle tone
-intrinsic stiffness
-background muscle tone - exists normally due to neural contributions (e.g. stretch reflex)
postural tone - activation of antigravity muscles
-examples: cutaneous, vestibular inputs
movement strategies (motor)

26
Q

reactive balance control

-most knowledge generated from…

A

studies using controlled balance disruptions (pertubations)

27
Q

reactive balance control: automatic postural response

  • defined as…
  • this is called
A

defined as synergistic activation of a group of muscle in a characteristic sequence to maintain equilibrium

  • latencies of muscle responses 80-120 ms (some as long as 160-200 ms)
  • reactive postural adjustment (RPA)
28
Q

short latency responses

-describe

A

nonfunctional
at spinal cord
could be a stretch reflex

29
Q

medium latency responses

-describe

A

functional

in midbrain/brainstem

30
Q

late-phase and latency responses

-describe

A

stepping, reaching

at cortex

31
Q

movement patterns used to recover balance in sagittal plane

-these strategies function along a…

A

ankle strategy
hip strategy
stepping or suspensory strategy
these strageties function along a continuum
-in slow movements, utilize primarily closed-loop control
-rapid movements require greater open-loop control

32
Q

RPA’s

  • adapt to…
  • set of muscles activated depends on…
A 
adapt to changes in the requirement for support
set of muscles activated depends on
-biomechanical support
-task exposure
-sensory conditions
33
Q

how to RPA’s change with biomechanical conditions?

A

with translation of wide surface, sequential activation of GAS/HS/PSP (ankle strategy)
with narrow bear, primary activation of proximal muscles (quad/abdomen (hip strategy))
ROM strength impairment will shift demand to other muscles/joints

34
Q

automatic postural responses: postural strategy modulates according to…

A

changing environmental support

repeated exposure to stimulus

35
Q

RPA’s and sensory conditions

-describe

A

RPA’s modulate according to sensory conditions

  • availability of sensory inputs
  • -muscle latencies to visual cues –> 200ms
  • -muscle latencies to somatosensory cues –> 80-100ms
36
Q

RPA’s modulate according to sensory conditions: sensory weighting hypothesis

  • describe
  • example
A

each sense provides unique contribution
the “gain,” or relative weight given to the sensory input by the brain, varies according to its accuracy as a reference point
example
-if touch becomes less reliable (peripheral neuropathy), visual inputs are weighted more heavily

37
Q

RPA’s adjust to situational predictability or…

A

learning

38
Q

RPA’s and learning: central set

  • defined as
  • organization of postural responses depends on…
  • with experience
A

defined as a state of the nervous system influenced by the context of the task
organization of postural responses depends on expectations of stability and/or perturbations
-in expected perturbations, postural responses are highly organized in a feed-forward control model, i.e. selected in advance
with experience, increased spatial organization/decreased EMG amplitude

39
Q

central set functional application to ACL injury

A

muscles become more organized and efficient at preventing shear forces

40
Q

anticipatory postural control

  • sometimes referred to as…
  • what are they
  • nervous system has…
A

anticipatory postural adjustments (APAs)
synergistic postural responses executed in advance of primary body movement
nervous system has advance knowledge

41
Q

anticipatory postural control

  • when do postural adjustments occur?
  • classic study found…
A

before action
study
-postural adjustments occur before activity
-raise arm to shoulder level
-80m sbefore deltoid contracts, lower back and leg extensors contract
-purpose: to stabilize the body to prevent shoulder movement from destabilizing the body (open-loop)

42
Q

anticipatory postural control

-postural adjustments accompany voluntary movements only…

A

when needed

43
Q

clinical applications for APAs

A

behavior context and speed of focal movement affect APAs

  • with fast movements, APAs are earlier and more reliable
  • greater movement resistance increases likelihood of APAs
  • external support reduces APAs
  • degreed of practice influences speed and accuracy of response

S2 Movement Science (13 decks)

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