Calcium ions bind with troponin molecules found on the tropomyosin protein and alter the structure of tropomyosin, exposing the cross bridge binding site on the actin.

Proper balance and posture are believed to depend on three systems which are

A muscle spindle consists of

Reflexes are automatic responses that are always monosynaptic

Stretch of the muscle spindle is relayed to the CNS via

Reflexes are automatic responses that either on or off and not graded to the strength of the input

Motor Units all contain the same number of muscle fibres

Visual and proprioceptive feedback are important for fine tasks but not simple balance