Control of Posture Flashcards
Define Posture
A composite of the positions of all the joints of the body at any given time
What is the Ideal Posture?
- Maintaining body in a stable condition
- Standing with little muscular effort
- Minimize stress and strain on tissue
How do we control posture with Reflexes?
- Simple Input-Output
- Stereotypical response
- Hard-Wired & cannot be changed
Example: Automatically stepping forward when you feel like you’re about to fall
How do we control posture by automatic responses?
- Typical responses that can be adapted
- Involves complex neural circuits
- Multiple Input - Output responses
- Can be re-shaped or re-programmed
What are three distinct aspects in postural control?
1) Postrual Orientation
2) Postural Equilibrium
3) Anticipatory Postural Adjustments
What is Postural Orientation (positioning body to perform a task)?
- Stability for arm or leg movement
- Keeping head steady while performing a task
- Considering involvement of biarticular muscles in a complex task
What is Postural Equilibrium ( Maintaining balance)?
- Staying at equilibrium
* using muscle activity to return to equilibirum
What can be defined by the Inverted Pendulum? Example for a 6ft. person?
If your center of gravity travels out of apex cone, you will fall.
Example:
6ft. person can only lean forward 8 degress
and backwards 4.5 degrees
What happens if we exceed the limits of stability?
Fall OR Move base of support
What is Postural Sway?
Humans generate a small amount of sway.
We can never stand completely still.
Why do we have Postural Sway?
1) Result of Noise:
tradeoff between energy cost and stability
2) Sway is Intentional by the CNS::
following reference point and exploring limits as we grow and change
What feedback do we use in Sensory Re-Weight
(using multiple sources to respond in changing conditions)?
Proprioception; Sensory Feedback is important in control of posture
What is the study found in children by (Bair et al. 2007)?
Children can re-weight multi-sensory input at around 4 years old
What does re-weighting rely on more?
Proprioception and vestibular input
What is Deadband of Sensory Feedback?
Taking no action if within in certain limits
Not moving if you’re not too far out to falling
Why does the nervous system have time delays?
Because of conduction of nervous impulses and processing information
What is the first to fire in a forward sway?
Gastrocnemius
What is to fire in backward sway?
Tibial
What helps define stability in stance?
Weight of mass on the base of support
What can be saves with automatic responses?
It can be reprogrammed after initial wrong response and learn by experience
What is Anticipatory Postural Adjustments? What patients are bad at making adjustments?
Counteracting instability from voluntary movements (Having body moving forward automatically when moving arm)
Parkinson patients
Why would adding a second task help improve someone’s ability to balance?
Small errors in balancing are ignored (deadband)
& Increases noise of feedback
What is Stochastic Resonance?
Adding in white noise to boost week signal detection
Example: Adding soles in shoes for old people to improve stability
