Chapter 7

Question 1

What is postural control?

Answer 1

Involves controlling the body’s position for the dual purpose of stability and orientation.

Question 2

Define postural orientation.

Answer 2

Ability to maintain an appropriate relationship between body segments, the body and the environment of the task.

Question 3

What does posture describe?

Answer 3

The biomechanical alignment of the body and its orientation in the environment.

Question 4

What is postural stability?

Answer 4

Ability to control centre of mass (COM) in relation to the base of support (BOS).

Question 5

What does COM stand for?

Answer 5

Centre of mass.

Question 6

How is COM determined?

Answer 6

By finding the weighted average of COM of each body segment.

Question 7

What does COG stand for?

Answer 7

Centre of gravity.

Question 8

Define BOS.

Answer 8

Area of body in contact with the support surface.

Question 9

What is COP?

Answer 9

Centre of pressure, which is the centre of distribution of total forces applied to the supporting surface.

Question 10

True or False: Stability and orientation demands are constant across all tasks.

Answer 10

False.

Question 11

What are muscle synergies?

Answer 11

Groups of muscles that work together to produce a specific movement or to stabilize the body during an activity.

Question 12

Define ataxia.

Answer 12

Lack of muscle coordination and control affecting movement, balance, and speech.

Question 13

What systems interact to determine our body’s position in space?

Answer 13

Musculoskeletal and neural systems.

Question 14

What is steady state balance?

Answer 14

The ability to control the COM relative to the BOS in fairly predictable and non-changing environments.

Question 15

Define reactive balance control.

Answer 15

Ability to recover a stable position following an unexpected perturbation.

Question 16

What is proactive (anticipatory) balance?

Answer 16

Ability to activate muscles in legs and trunk in advance for balance control during potential destabilizing voluntary movements.

Question 17

What is feedback control in postural control?

Answer 17

Postural control occurring in response to sensory feedback from external perturbation.

Question 18

Define feedforward control.

Answer 18

Anticipatory postural adjustments made in anticipation of a voluntary movement that could potentially destabilize posture.

Question 19

Which brain areas are involved in higher level planning for balance?

Answer 19

Frontal and motor cortex.

Question 20

What is static balance?

Answer 20

Stability underlying quietly sitting or standing, which is dynamic because of postural sway.

Question 21

What factors help maintain postural sway within BOS?

Answer 21

• Body alignment
• Muscle tone

Question 22

What is muscle tone?

Answer 22

Force with which a muscle resists being lengthened (its stiffness).

Question 23

How is postural tone defined?

Answer 23

Activity that increases in antigravity postural muscles to counteract the force of gravity.

Question 24

What reduces postural tone?

Answer 24

Lesions to the dorsal (sensory) roots of the spinal cord.

Question 25

What is Berg’s balance scale (BBS)?

Answer 25

Test a patient's ability to sit or stand independently.

Question 26

What is an ankle strategy?

Answer 26

Restores the COM to a position of stability through body movement primarily centred around the ankle joints.

Question 27

What does the hip strategy control?

Answer 27

Motion of COM by producing large and rapid motion of the hip joints with antiphase rotation of the ankles.

Question 28

Define change in support strategies.

Answer 28

Rapid moving of limbs to change BOS, such as taking a step or reaching out and grasping.

Question 29

What does APA stand for?

Answer 29

Anticipatory postural adjustment.

Question 30

What is adaptation in the context of postural control?

Answer 30

Refining and tuning movements in response to task demands.

Question 31

What is tonic muscle activity?

Answer 31

Continuous, low-level contraction of muscles to maintain posture and stability.

Question 32

What is phasic muscle activity?

Answer 32

Short bursts of contraction tuned in the direction of instability.

Question 33

List the sensory inputs for steady state balance.

Answer 33

* Visual * Somatosensory * Vestibular

Question 34

What does the visual system provide for balance?

Answer 34

Information regarding the position and motion of the head with respect to surrounding objects and as a reference for verticality.

Question 35

What does the somatosensory system provide?

Answer 35

Information about position and motion of the body with reference to supporting surfaces.

Question 36

What does the vestibular system inform the CNS about?

Answer 36

Position and movement of the head with respect to gravity and inertial forces.