Henry Family Blog

Purposeful human movement is governed by interrelated feedforward and feedback control loops.  A feedforward loop is an open loop in the Central Nervous System that provides output independent of sensory input or movement outcomes.   There must be knowledge of the system and the surroundings.  A feedback loop is a closed loop where sensory input is processed to generate or refine movement commands.  Meaning, the Central Nervous System changes the output based on sensory input. 

Sensory information from internal and external environments is essential for initiation and regulation of movement.  You must know the state of the body, the state of the environment and the state of the body with respect to the environment. 

Your sensory information is integrated by the Central Nervous System into two types of information critical to neuromuscular control.  the two types are Proprioception and Kinesthesia.  Proprioception is joint position sense and spatial orientation of body segments.  Kinesthesia is sensation of joint motion.

There are multiple ways to transfer sensory information to the Central Nervous System.  These ways are visual, audition, tenomuscular receptors, articular receptors and cutaneous receptors.  Of these, vision provides the most important sensory information regarding external environment.  It is not essential for movement but accuracy is greatly impaired without it.  Vision takes a role in planning and executing movement with target and obstacle identification.  It is essential for error correction.  Audition refines motor control and aids in preparing the neuromuscular system for activity.  It includes speech, proper use of electronics, terrain during gait and object integrity.  It is not required for the production of voluntary movement.

Tenomuscular receptors are muscle spindles and golgi tendon organ.  The muscle spindle is sensitive to muscle length.  It is an indirect indication of joint position sense and kinesthesia.  They are efferent innervated by the beta and gamma motorneurons.  During a contraction, the equatorial region lengthens and excites the 1a afferent.  The golgi tendon organ is sensitive to muscle tension.  It is an indication of the muscle activation status.  It is an indirect indication of joint position sense and kinesthesia.  It has limited usefulness due to multiple levels of sensory input at the same joint position.

Articular receptors are sensitive to joint displacement, velocity and acceleration.  They have an indirect indication of joint position and kinesthesia.  They are also sensitive to joint tension and compression.  Cutaneous receptors are sensitive to touch, pain and temperature.  They are essential because of the precision control of grip force.  The pressure receptors contribute to joint position sense and kinesthesia.  In isolation, each source of sensory information relevant to proprioception and kinesthesia is insufficient. 
 

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