Table 2. Components of balance control.

Sensory system	CNS	Motor system
Afferent input	Organization of sensory input and choice and triggering of motor responses	Efferent output
Somatosensory system: - proprioceptors: muscle  spindle type I and II, Golgi  tendon organ, joint receptors - cutaneous and subcutaneous  receptors Vision: - retina Vestibular system: - semicircular canals and  otholiths in the inner ear	Myotatic stretch reflex Long-loop reflexes  Internal representations Learned skills Synergistic action Sensory strategies Adaptive mechanisms Anticipatory mechanisms	Reflexes Automatic movements Voluntary movements  Muscles of the upper and lower extremities Trunk and neck muscles Neuromuscular synergies: - ankle strategy - hip strategy - stepping strategy - mixed strategy