Postural Control Flashcards
Postural control emerges from the interaction of what 3 things?
- task
- individual
- environment
The ability to control our body’s position in space emerges from a complex interaction of musculoskeletal and neural systems is referred to as what?
the postural control system
What can be defined as “controlling the body’s position in space for the dual purposes of stability and orientation”?
postural control
What can be defined as “the ability to maintain an appropriate relationship between the body segments, and between the body and the environment”?
Postural orientation
What can be defined as the ability to control the center of mass in relationship to the base of support?
postural stability
What is the center of mass?
A point that is at the center of the total body mass, which is determined by finding the weighted average of the COM of each body segment
The vertical position of the COM is called what?
The center of gravity
Define the base of support
The area of the body that is in contact with the support surface
What can be defined as the center of the distribution of the total force applied to the supporting surface?
The center of Pressure
All tasks consist of what 2 components?
a stability component and a orientation component
*Orientation and stability demands change with each task
What is the clinical definition of a fall?
an event that results in a person coming to rest inadvertently on the ground (unplanned or unexpected contact with a supporting surface)
What is the research definition of a fall?
movement of the COM outside of the base of support (including stepping to recover stability)
What factors contribute to our stability during quiet stance?
- body alignment
- muscle tone
- postural tone
Describe perfect alignment
- mastoid process
- a point just in front of the shoulders
- the hip joints (or just behind)
- a point just in front of the center of the knee joints
- a point just in front of the ankle joints
What is muscle tone?
The force with which a muscle resists being lengthened (stiffness)
What 3 things contribute to our background muscle tone?
- the intrinsic stiffness of the muscles themselves
- the background muscle tone, which exists normally in all muscles because of neural contributions
- postural tone
Define postural tone
the activation of antigravity muscles during quiet stance
Lesions to what area of the spinal cord result in reduce postural tone. What does this signify?
Dorsal column
The importance of somatosensory inputs to postural tone
What are 6 movement strategies to maintain balance?
- Controlling body sway
- Feedback control
- Feedforward (anticipatory) control
- Anteroposterior stability
- Lateral stability
- Multidirectional stability
How is body sway controlled?
The CoP works to control the CoM moving the body backward and forward.
What does feedback control refer to?
postural control that occurs in response to sensory feedback from an external perturbation
What are 2 examples of when feedback control is needed to maintain balance?
- when the support surface moves
- when there are disruptions to gait
What does feedforward control refer to?
postural responses that are made in anticipation of a voluntary movement that is potentially destabilizing in order to maintain stability during the movement
What are 2 examples of when feedforward control is needed to maintain balance?
- prior to a voluntary movement that is potentially destabilizing (lifting a heavy object)
- during volitional COM movements in stance
What is a synergy?
A functional coupling of groups of muscles that are constrained to ACT TEGETHER as a unit
What are the 3 postural movement strategies used by normal adults for controlling anteroposterior sway?
- ankle
- hip
- stepping
Which muscles are activated during forward sway when utilizing the ankle strategy?
- paraspinal muscles
- gastroc
- hamstrings
Which muscles are activated during backwayd sway when utilizing the ankle strategy?
- abdominals
- quads
- tibialis anterior
Muscle activity during the ankle strategy begins in the _____ muscles, followed by activation of the _____ muscles
distal
proximal
Which muscles are activated during forward sway when utilizing the hip strategy?
- abdominals
- quads
Which muscles are activated during backward sway when utilizing the hip strategy?
- paraspinal
- hamstrings
When is the hip strategy used over the ankle strategy?
- in response to larger, faster perturbations
- when the support surface is smaller than the feet
Muscle activity during the hip strategy begins in the _____ muscles, followed by activation of the _____ muscles
proximal
distal
Which strategy is used when the ankle and hip strategies are not enough to maintain balance?
stepping strategy
What type of stability is used to recover stability in a mediolateral direction?
lateral stability pattern
What muscles are used to maintain ML stability?
muscles at the hip and trunk
Muscle patterns are organized in a ______-to-______ direction during lateral stability
proximal-to-distal
Which brain structure is in control of adaptation?
the cerebellum
How does the cerebellum control adaptation?
It modifies postural muscle amplitude in response to changing tasks and environmental conditions
Which brain structure is in control of postural set?
the basal ganglia
How does the basal ganglia control postural set?
By quickly changing muscle patterns in response to changing tasks and environmental conditions
How does the brainstem contribute to postural control?
- regulates postural tone
- integrates sensory information
- contributes to anticipatory postural control accompanying movements
Effective postural control requires more than the ability to generate and apply forces for controlling the body’s position in space, we must know when and how to apply restoring forces. What is responsible for this?
perceptual systems within the CNS which develop a picture of where the body is in space and whether the body is stationary or in motion
Which 3 systems detect the body’s position and movement is space with respect to gravity and the environment?
- visual
- somatosensory
- vestibular
Visual inputs provide information regarding what?
The position and motion of the head with respect to surrounding objects as well as a reference for verticality
Visual inputs include what 2 types of information?
- peripheral visual information
- foveal information
What 2 things does the somatosensory system provide to the CNS?
- position and motion information about the body with reference to the BOS
- information about the relationship of body segments to one another
What does the vestibular system provide the CNS with?
Information about the position and movement of the head with respect to gravity and inertial forces
Can vestibular signals alone provide the CNS with a true picture of how the body is moving in space? Why or why not?
No, because it cannot distinguish between a simple head nod and a forward bend
Vestibular inputs also provide information regarding _____ acceleration of the head
angular
In summary _____ inputs provide a relationship of our body to the environment
visual
In summary _____ inputs provide information regarding the surface of support
somatosensory
In summary _____ inputs provide information regarding gravity
vestibular
What does the sensory weighting hypothesis state?
When one sensory system is less reliable, the input to the CNS from that system is weighted less heavily, and inputs from other systems will be weighted more heavily
What are the 6 sensory conditions to test sensory organization?
1) stable surface eyes open
2) stable surface eyes closed
3) stable surface with dome over head
4) unstable surface eyes open
5) unstable surface eyes closed
6) unstable surface with dome over head
Which test helps determine which sensory system an individual relies on to maintain balance?
Clinical Test of Sensory Interaction in Balance (CTSIB)
