Lecture 10

Question 1

What is seen in action potentials between cue only and when a startle response is given?

Answer 1

Both APA and step initiation were speeded by the Startle (acoustic cue), movement occurs faster, far too fast for voluntary movement

Question 2

APA during expected external pertubation

Answer 2

can generate anticipatory response for an external pertubation, corrections are already in place to correct for the pertubation

Question 3

define reactive balance control

Answer 3

balance responses that occur in reaction to an unexpected disturbance
eg. push or pull, translation, or rotation

Question 4

dynamic posturograohy and reactive balance control

Answer 4

can use machines that push or pull, or suddenly drop weights
translation: move platform fowards and backwards
rotation: can tilt feet up or down, and side to side

Question 5

Postural strategy

Answer 5

CNS selects the “way” it will respond to reach a goal

Question 6

Goals of postural strategy

Answer 6

restore balance (COM within BOS)

Question 7

Different types of postural strategies

Answer 7

Fixed support: do whatever it takes to maintain balance without moving feet or holding on to a rail
Change-in-support: response includes shift in BOS

Question 8

Postural synergy

Answer 8

specific patterns of muscle activity used to implement a strategy

Question 9

Fixed Support Strategies

Answer 9

not changing BOS by moving feet or holding onto support

Question 10

What happens during fixed support strategies

Answer 10

when pertubated from stable state, can slow down the COM movement (to some extent) by rapidly generating torque at ankles, hips or other joints

Question 11

Ankle strategy

Answer 11

form of fixed support strategy, body moves as a single unit around ankle joints
inverted pendulum

Question 12

When are ankle strategies seen

Answer 12

in response to small disturbances

Question 13

To use an ankle strategy, we need?

Answer 13

Adequate ROM + Strength at ankle joints
Firm, broad surface below the feet

Question 14

Hip strategy

Answer 14

body moves about the hip joints
“double pendulum” out of phase movement, upper and lower body moves in OPPOSITE directions

Question 15

When are hip strategies seen

Answer 15

in response to LARGE disturbances
support surface is narrow

Question 16

to use a hip strategy, we need?

Answer 16

Adequate ROM + strength in the hip region

Question 17

in most scenarios what strategies are used?

Answer 17

Combination of ankle and hip strategies plus other joints are brought in as well

Question 18

postural syergies definition

Answer 18

refers to well defined temporal and spatial patterns of leg and trunk muscle activations used to preserve upright stance

Question 19

T/F: spinal reflexes are more complex than postural synergies

Answer 19

false, as adaptable to changes in context, are directionally specific, and can be learned

Question 20

what do postural synergies involve

Answer 20

balance correcting responses or APAS

Question 21

What is the latency of posteral synergy

Answer 21

around 100ms from onset of pertubation

Question 22

T/F voluntary reaction time is longer latency than postural synergy

Answer 22

true, voluntary is 200-500ms whereas postural synergy is 100ms

Question 23

T/F spinal reflexes are longer than postural synergy

Answer 23

false, spinal reflex latency is 30ms, compared to 100ms

Question 24

Why are postural synergies longer than spinal reflexes

Answer 24

added time involves supraspinal circuits
APRs may be aided or opposed by spinal reflexes
Followed by a later onset, voluntary activity