Balance And Posture

Question 1

What does the centre of pressure do

Answer 1

It actively oscillates forward/back to maintain the centre of mass within the limits of stability

Question 2

Why do we sway when standing

Answer 2

1. Sensory estimation- imperfect process with sensor noise
   2.motor output- also an imperfect process
2. External/internal perturbations e.g. breathing

Question 3

What info keeps us upright?

Answer 3

1.vision
2.proprioception
3.vestibular apparatus
4.touch

Question 4

Quality of visual information:

Answer 4

Closer objects are more useful for controlling away as their is a greater image displacement on the retina

Distant visual information effectively useless for balance- no retinal motion. May as well be blind when standing on a cliff edge

Question 5

What is motion parallax

Answer 5

Objects appear to move relative to each other depending on the focus point

Question 6

What is visual vection

Answer 6

A false sense of motion induced by a moving scene eg watching an adjacent train depart the station u may get the impression that your train has started to move

Question 7

What is the effect of sensory removal on postural responses

Answer 7

Standing is possible but only with Proprioceptive input. However balance reflexes are more effective with all senses available

Question 8

Motor output for standing:

Answer 8

Continuous calf muscle contractions prevent us falling forwards

Question 9

Is passive ankle stiffness sufficient enough to maintain balance

Answer 9

No, active modulation is required