Balance and Vestibular Intro-to be continued

Postural Stability definition

the dynamic process by which the body’s position is maintained in equilibrium

Equilibrium definition

Includes states of rest (static) or steady-state motion (dynamic)

Balance definition

Ability to maintain COM within BOS in a variety of environments and in the context of the task performance

When is balance greatest?

when COM or COG is maintained over base of support

What does balance include?

Includes reactive and anticipatory balance reactions

Dynamic multi-system control of balance

A.      Nervous System

• Sensory processing

• Sensory motor integration

•     Motor strategies

B.      Musculoskeletal System

C.      Contextual Effects

Sensory Processing definition

perception of body orientation based on peripheral sensory inputs - visual, somatosensory, and vestibular information

Visual processing

• Required for utilization of Anticipatory Postural Adjustments/Feed Forward System

• < 7 yo rely on vision and elderly (70+) – slower reaction times = slower movements

Types of vision

• Central/foveal

• Peripheral/ambient

Central/foveal vision

Environmental info- context, obstacles, and verticality

Peripheral/ambient vision

• No conscious attention, subconscious sensory input

•   Detects movement, but cannot decipher if it is movement of oneself or the environment

• Spatial info – direction and speed of movement, motion

• Orientation of the head to maintain level gaze

Examples of conditions affecting visual processing

Macular degeneration, blindness, glaucoma, cataracts, diabetic retinopathy

Purpose of somatosensation

• provides information about position and motion of the body and body segments relative to each other and the support surfaces

Somatosensation is:

•   > 7 yo – dominant system for postural stability, esp. in reactive balance (unexpected perturbations/automatic postural responses)

• More reliable (quicker), maturation of the ascending/descending pathways

What are the receptors of somatosensation?

• Muscle spindles

• Golgi tendon organs (GTOs)

• Joint mechanoreceptors

• Skin mechanoreceptors

Muscle spindles

Detect muscle length and changes in muscle length; major contributor to joint position and movement sense.

Golgi tendon organs (GTOs)

Detect muscle tension/force and contribute to proprioceptive feedback and regulation of muscle activity.

Joint mechanoreceptors

Receptors in joint capsules and ligaments that detect joint position, movement, and mechanical stress, particularly near the extremes of joint range.

Skin mechanoreceptors

vibration, light touch, deep pressure, skin stretch

Injuries such as recurrent ankle sprain, knee ligament injury, DJD have shown _______ postural sway compared to normal, but is unclear whether the _______ joint position sense is from changes in ______ receptor or _______ receptors

Increased; Decreased; Joint; Muscle

Examples of conditions that affect somatosensation

peripheral neuropathy (DM, chemo), CVA, amputation

Vestibular purpose

Provides information about the position and movement of the head with respect to gravity (not with respect to the body)

• Ex: cannot distinguish lateral flexion from sidelying

• Requires information from mechanoreceptors of the spine for differentiation