Postural Control Flashcards
postural control
- maintaining body alignment
- maintaining balance in the face of external disturbing forces such as gravity
- maintaining balance in the face of self-generated forces during movement
3 developmental progressions
- head control
- sit
- stand
head control
hold steady while moving, back muscles activate
sit
sits without support, sits alone with good coordination, and gets to sitting (lying -> sitting)
stand
pulls to standing, stands alone
3 developmental progression trends
- cephalocaudal progression of control of joints
- flex dominated positions -> extensor dominated positions
sway
motion about a central equilibrium axis, disturbance -> system not mature
3 main classes of sensors
vision, vestibular sensors, somatosensors/body sensors
vision sensors
take images in, what we see, whats going on around the head, interpreted in brain (in head)
vestibular sensors
linear, rotational movement, inner ear (in head)
somatosensors/body sensors
receptors found in muscle used to help determined position in rest of the body
CNS uses combination of these 3 systems to rapidly figure out..
why swaying, how much sway, and then what muscles need to contract to fix it
we know from milestones..
- postural control progresses from head/shoulders (1 joint)
only need first 2 sensors - to sitting (2 joints)
- to standing (many joints)
- brain needs to relearn for each new stage
visual dominance during stage 1
development of head control
how do we know a newborn is developing visual dominance?
- newborn in room with vertical stripes
–stripes twist
–neck muscles contract as if trying to follow the movement of the stripes - if visual info is blocked and body or head is twisted, don’t get the same response
- therefore, at this stage, infant has a visually dominant system
- no evidence of vestibular or somatosensory sensors until several months later
early head/neck control
not limited by inadequate strength (learn to take in appropriate sensory info)
~3-4 months
- child will exhibit an appropriate neck response to sway 40-60% of the time
- something has to happen between 3-4 months and 6-7 months, when the infant can sit upright
~ 6 months
- infant reaches “sloppy sitting” (hunched/leaning on belly) milestone
— ignoring body info
— independent sitting is more complicated
— 2 joints to control
— interaction torque - sway control begins to appear 6-7 months
— using sensory signals from the neck to control the head - not exclusively visually dominant for head control *
- start to trust somatosensors (rely on visual sensors first)
independent sitting requires..
head plus trunk control, plus the ability to control sway (motion about a vertical equilibrium axis)
sway control during upright sitting appears around 6-7 months
- appropriate neck muscle responses to induced sway occur 40-60% of the time by 3-4 months
- by 5-8 months, neck muscle responses become progressively coordinated with trunk responses
sensory information for sitting
vision dominates early and gradually gives way to somatosensory information from the hips (starting to trust)
moving room - sitting
- adult: nothing would happen in moving box bc system is mature
- sitting infant: will fall when box is moved
— behavior continues from about 3 months after milestone is reached
— after 3 months, infant trusts somatosensors instead of visual sensors
independent stance
- strength doesn’t limit development
- coordinated muscle responses to platform disturbances
- vision is first source of sensory information and lessens in dominance in experienced walkers
- somatosensory info to muscles controlling stance occurs around 9 months and strengthens as walking experience accumulates
moving room - standing
- child is upright and independently controlling sway ~11-12 months of age
- put in room while standing: child will fall for about 3 months, new milestones revert back to visual sensors
