NM Ch. 7: Normal Postural Control

postural control

controlling bodies position in space for dual purposes of stability and orientation

postural stability

ability to control center of mass in relationship to the base of support

COM (center of mass)

point at the center of total body mass. around the middle of the individual

BOS (base of support)

area of the body in contact with the support surface

COG (Center of gravity)

vertical projection of the COM

COP (center of pressure)

center of distribution of the total force applied to the supporting surface (ex: think about standing in heels versus flat shoes)

postural orientation

ability to maintain relationship between the body segments and between the body and the environment for a task

ability to control body position in space

(part of individual system) complex interaction of musculoskeletal and neural systems

músculoskeletal components of postural control

(part of individual system) joints, spine, muscles, and biomechanical relationships

neural components of postural control

(part of individual system) motor processes, sensory processes, and higher-level cognitive processes 

task constraints of postural control include: 

steady-state, reactive, proactive

steady state

the ability to control the COM relative to the BOS in fairly predictable and nonchanging conditions

reactive

the ability to recover a stable position following an unexpected disturbance. feedback mechanism

proactive

the ability to activate muscles in the legs and trunk for balance control in advance of potentially destabilizing voluntary movements. feedforward mechanism

Feedback control

occurs in response to sensory feedback from something external

feedforward control

anticipatory postural adjustments made in anticipation of a voluntary movement

stability limits

point at which a person will change the configuration of BOS to achieve stability (think about demo with falling)

motor patterns of reactive balance control

ankle, hip, step, and reach-to-grasp

reactive balance control

postural synergies are not fixed, stereotypical reactions. refined and tuned in response to changing demands in task and environment.

adaptation

refining and tuning movements in response to task demands

proactive balance control

central nervous system uses anticipatory processes in controlling action. postural activity anticipates voluntary movement.

proactive balance in sitting…

…preparing to stand from sitting

sensory inputs for steady state balance

vision (position and motion of head, verticalness, information), somatosensory (provides CNS with position and motion information about body, reports info about relationship of body segments to one another) and vestibular

what does sensory integration in steady state balance mean?

CNS is able to modify importance of any one sense for postural control

task dependent sensory reweighting

CNS reweights sensory information under changing task conditions. happens during learning of new motor skills, ex: when you have to stand on one foot with your eyes closed

visual information for reactive balance

gathered as a person enters an environment to form a map of environmental obstacles

somatosensory inputs for reactive balance

controlling body sway when there is imbalance caused by rapid displacements of the support surface

attentional resources

information processing resources required to complete a task

dual-task interference

two tasks performed simultaneously; attentional resources may decrease performance on one or more tasks

most important brain structures for postural control

spinal cord and brainstem