Chapter 7 Flashcards
Normal postural control
What is postural control?
Involves controlling the body’s position for the dual purpose of stability and orientation.
Define postural orientation.
Ability to maintain an appropriate relationship between body segments, the body and the environment of the task.
What does posture describe?
The biomechanical alignment of the body and its orientation in the environment.
What is postural stability?
Ability to control centre of mass (COM) in relation to the base of support (BOS).
What does COM stand for?
Centre of mass.
How is COM determined?
By finding the weighted average of COM of each body segment.
What does COG stand for?
Centre of gravity.
Define BOS.
Area of body in contact with the support surface.
What is COP?
Centre of pressure, which is the centre of distribution of total forces applied to the supporting surface.
True or False: Stability and orientation demands are constant across all tasks.
False.
What are muscle synergies?
Groups of muscles that work together to produce a specific movement or to stabilize the body during an activity.
Define ataxia.
Lack of muscle coordination and control affecting movement, balance, and speech.
What systems interact to determine our body’s position in space?
Musculoskeletal and neural systems.
What is steady state balance?
The ability to control the COM relative to the BOS in fairly predictable and non-changing environments.
Define reactive balance control.
Ability to recover a stable position following an unexpected perturbation.
What is proactive (anticipatory) balance?
Ability to activate muscles in legs and trunk in advance for balance control during potential destabilizing voluntary movements.
What is feedback control in postural control?
Postural control occurring in response to sensory feedback from external perturbation.
Define feedforward control.
Anticipatory postural adjustments made in anticipation of a voluntary movement that could potentially destabilize posture.
Which brain areas are involved in higher level planning for balance?
Frontal and motor cortex.
What is static balance?
Stability underlying quietly sitting or standing, which is dynamic because of postural sway.
What factors help maintain postural sway within BOS?
- Body alignment
- Muscle tone
What is muscle tone?
Force with which a muscle resists being lengthened (its stiffness).
How is postural tone defined?
Activity that increases in antigravity postural muscles to counteract the force of gravity.
What reduces postural tone?
Lesions to the dorsal (sensory) roots of the spinal cord.
What is Berg’s balance scale (BBS)?
Test a patient’s ability to sit or stand independently.
What is an ankle strategy?
Restores the COM to a position of stability through body movement primarily centred around the ankle joints.
What does the hip strategy control?
Motion of COM by producing large and rapid motion of the hip joints with antiphase rotation of the ankles.
Define change in support strategies.
Rapid moving of limbs to change BOS, such as taking a step or reaching out and grasping.
What does APA stand for?
Anticipatory postural adjustment.
What is adaptation in the context of postural control?
Refining and tuning movements in response to task demands.
What is tonic muscle activity?
Continuous, low-level contraction of muscles to maintain posture and stability.
What is phasic muscle activity?
Short bursts of contraction tuned in the direction of instability.
List the sensory inputs for steady state balance.
- Visual
- Somatosensory
- Vestibular
What does the visual system provide for balance?
Information regarding the position and motion of the head with respect to surrounding objects and as a reference for verticality.
What does the somatosensory system provide?
Information about position and motion of the body with reference to supporting surfaces.
What does the vestibular system inform the CNS about?
Position and movement of the head with respect to gravity and inertial forces.
