Muscle Spindles: Their Messages and Their Fusimotor Supply

<jats:title>Abstract</jats:title><jats:p>The sections in this article are:</jats:p><jats:sec><jats:title>Tendon Organs</jats:title></jats:sec><jats:sec><jats:title>Structure of Muscle Spindles</jats:title><jats:sec><jats:title>Classic View</jats:title></jats:sec><jats:sec><jats:title>Recognition of Motor Duality</jats:title></jats:sec><jats:sec><jats:title>Subdivision of Nuclear‐Bag Fibers</jats:title></jats:sec></jats:sec><jats:sec><jats:title>Functional Properties of Primary and Secondary Spindle Afferent Endings</jats:title><jats:sec><jats:title>Different Responses to Various Stimuli</jats:title></jats:sec><jats:sec><jats:title>Mode of Summation of Signal Components</jats:title></jats:sec><jats:sec><jats:title>Amplitude Nonlinearity</jats:title></jats:sec><jats:sec><jats:title>Linear Responses to Sinusoidal Stretching</jats:title></jats:sec><jats:sec><jats:title>Assessment</jats:title></jats:sec><jats:sec><jats:title>Possible Intermediate Endings</jats:title></jats:sec></jats:sec><jats:sec><jats:title>Motor Supply to Muscle Spindle</jats:title><jats:sec><jats:title>Gamma Motor Axons</jats:title></jats:sec><jats:sec><jats:title>Delimitation of Static and Dynamic Fusimotor Axons</jats:title></jats:sec><jats:sec><jats:title>Intrafusal Destination of Static and Dynamic Axons</jats:title></jats:sec><jats:sec><jats:title>Properties of Intrafusal Muscle Fibers</jats:title></jats:sec><jats:sec><jats:title>Beta or Skeletofusimotor Axons</jats:title></jats:sec></jats:sec><jats:sec><jats:title>Possible Functional Roles for the Fusimotor System</jats:title><jats:sec><jats:title>Maintenance of Sensitivity</jats:title></jats:sec><jats:sec><jats:title>Central Regulation of Spindle Sensitivity (Parameter Control)</jats:title></jats:sec><jats:sec><jats:title>Fusimotor Biasing and Suggested Role as Servo Input</jats:title></jats:sec><jats:sec><jats:title>Assessment</jats:title></jats:sec></jats:sec><jats:sec><jats:title>Summary</jats:title><jats:sec><jats:title>Structure</jats:title></jats:sec><jats:sec><jats:title>Functional Differences Between Primary and Secondary Endings</jats:title></jats:sec><jats:sec><jats:title>Static and Dynamic Fusimotor Axons</jats:title></jats:sec><jats:sec><jats:title>Possible Functional Roles for the Fusimotor System</jats:title></jats:sec></jats:sec>