Intro | Golgi Tendon Organ | Motor Neuron | Muscle | Muscle Spindle | Sensory Neurons | Tendon
Part 1: Image-Mapped Tutorial
Part 2: Matching Self-Test
Part 3: Multiple-Choice Self-Test
Return to main tutorial page
Sensory Neurons carry information from the proprioceptive receptors via the dorsal root of the spinal cord to the ventral horn of the spinal cord where they synapse on motor neurons. The muscle spindle afferent neurons are activated when the intrafusal fibers they are embedded within are stretched or lengthened due to an externally applied force. Conversely, the Golgi tendon organ afferent neurons are activated when tension or contraction within the attached muscle increases suddenly.
Two different classes of sensory or afferent neurons are associated with the muscle spindles (Parent, 1996). Group 1a, or the primary afferents, supply all three types of intrafusal fibers. These large sensory fibers wrap around the central region of a muscle spindle in a spiral arrangement. Primary afferents are the most sensitive to the rapidly changing length of fibers, firing at a higher rate during change than during steady-state conditions (thereby encoding velocity). Group II, or the secondary afferents, are small fibers that supply only a subclass of intrafusal fibers, the static nuclear bag fibers. These sensory fibers are sensitive to length. Only one type of sensory or afferent neuron is associated with the Golgi tendon organ. These group 1b, afferent fibers branch extensively and wrap around the many collagen fibers that compose the Golgi tendon organ.
Parent, A. (1996). Carpenter's human neuroanatomy (9th ed.). London: Williams & Wilkins.