Muscle Spindles: Their Messages and Their Fusimotor Supply

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