Control of Posture

Question 1

Define Posture

Answer 1

A composite of the positions of all the joints of the body at any given time

Question 2

What is the Ideal Posture?

Answer 2

• Maintaining body in a stable condition
• Standing with little muscular effort
• Minimize stress and strain on tissue

Question 3

How do we control posture with Reflexes?

Answer 3

• Simple Input-Output
• Stereotypical response
• Hard-Wired & cannot be changed

Example: Automatically stepping forward when you feel like you’re about to fall

Question 4

How do we control posture by automatic responses?

Answer 4

• Typical responses that can be adapted
• Involves complex neural circuits
• Multiple Input - Output responses
• Can be re-shaped or re-programmed

Question 5

What are three distinct aspects in postural control?

Answer 5

1) Postrual Orientation
2) Postural Equilibrium
3) Anticipatory Postural Adjustments

Question 6

What is Postural Orientation (positioning body to perform a task)?

Answer 6

• Stability for arm or leg movement
• Keeping head steady while performing a task
• Considering involvement of biarticular muscles in a complex task

Question 7

What is Postural Equilibrium ( Maintaining balance)?

Answer 7

• Staying at equilibrium

* using muscle activity to return to equilibirum

Question 8

What can be defined by the Inverted Pendulum? Example for a 6ft. person?

Answer 8

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

Question 9

What happens if we exceed the limits of stability?

Answer 9

Fall OR Move base of support

Question 10

What is Postural Sway?

Answer 10

Humans generate a small amount of sway.

We can never stand completely still.

Question 11

Why do we have Postural Sway?

Answer 11

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

Question 12

What feedback do we use in Sensory Re-Weight

(using multiple sources to respond in changing conditions)?

Answer 12

Proprioception; Sensory Feedback is important in control of posture

Question 13

What is the study found in children by (Bair et al. 2007)?

Answer 13

Children can re-weight multi-sensory input at around 4 years old

Question 14

What does re-weighting rely on more?

Answer 14

Proprioception and vestibular input

Question 15

What is Deadband of Sensory Feedback?

Answer 15

Taking no action if within in certain limits

Not moving if you’re not too far out to falling

Question 16

Why does the nervous system have time delays?

Answer 16

Because of conduction of nervous impulses and processing information

Question 17

What is the first to fire in a forward sway?

Answer 17

Gastrocnemius

Question 18

What is to fire in backward sway?

Answer 18

Tibial

Question 19

What helps define stability in stance?

Answer 19

Weight of mass on the base of support

Question 20

What can be saves with automatic responses?

Answer 20

It can be reprogrammed after initial wrong response and learn by experience

Question 21

What is Anticipatory Postural Adjustments? What patients are bad at making adjustments?

Answer 21

Counteracting instability from voluntary movements (Having body moving forward automatically when moving arm)

Parkinson patients

Question 22

Why would adding a second task help improve someone’s ability to balance?

Answer 22

Small errors in balancing are ignored (deadband)

& Increases noise of feedback

Question 23

What is Stochastic Resonance?

Answer 23

Adding in white noise to boost week signal detection

Example: Adding soles in shoes for old people to improve stability