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.
