Postural control and reflexes Flashcards
Week 4
Center of mass:
Weighted average of COM of each body segment in 3D space. Changes depending on how body moves.
Center of gravity:
Vertical projection of COM onto ground
Center of pressure:
Point location of body on floor
To maintain balance we need to:
Keep the body’s COM within the base of support
Neurones involved in the myotactic reflex:
- Ia afferent (sensory info about spindle stretch)
- Alpha motor (motor signal to contract muscle)
- Gamma motor neurone (regulates the sensitivity of afferents to stretch -by controlling fibres of muscle spindle itself)
Name of the model that, when standing there is a slight anterior-posterior movement about the ankle.
Inverted pendulum model
Name 3 postural strategies:
- Ankle
- Hip
- Stepping
Strategy for smaller, slower perturbations
Ankle strategy
2 models of balance:
- Reflex model
- Systems model
Reflex model of balance
Postural responses to perturbations arise by reflex pathway activations thanks to info from sensory receptors.
What was is information flow in the reflex model
Unidirectional
Systems model of balance:
Not one system that controls but a combination of systems. CNS located body’s COG and adaptively organises its response.
Response in the systems model is based on:
- Body’s biomechanics constraints
- Available sensory information
- Environment
- Prior experience
4 sensory components of balance:
Somatosensory
Proprioception
Visual
Vestibular
What do we use to measure postural control?
Posturography (static or dynamic)
