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Organization Of The Motor Systems


Organization Of The Motor Systems
The motor systems are those areas of the nervous system that are primarily responsible for controlling movement. The movement can either be:

        Guided by inputs from the sensory systems (closed-loop or reflex controlled); or
    Triggered by a sensory cue or some internal desire to move (open- loop or volitional movement).
In practice, most motor acts involve both types of movement.
Closed-loop movements predominantly involve the axial or proximal muscles responsible for balance, posture and locomotion, while the open-loop movements are typically associated with the distal musculature concerned with the control of fine skilled movements.
The organization of the motor structures is best viewed in terms of a hierarchy.


A cautionary note
It is important to remember that the division of the central nervous system into motor and sensory functions is a gross simplification as all the motor areas have some sensory input. It is difficult to know the point at which a highly processed sensory input becomes the impulse for the initiation of a movement. It should also be realized that the division of the motor systems into various levels and different motor pools is a convenient but not strictly accurate device for understanding the control of movement and the pathophysiology of disorders of the motor system.