KINE 3020 Chapter Notes -Gamma Motor Neuron, Extrafusal Muscle Fiber, Intrafusal Muscle Fiber
4 Dec 2013
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Systems 1: control of muscle/ topic 4: sensory. Nuclear bag (divided into both static and dynamic types) Fiber has many spherical nuclei in its central noncontractile region (looking like an elastic bag of nuclei) which stretches quickly when lengthened because of its elasticity. The group ii endings wrap around the region next to the equator, which is less elastic and thus less responsive to stretching. When a muscle is stretched, it stretches the muscle spindle, exciting the ia afferent neurons. The spinal stretch reflex is activated by excitatory monosynaptic connections from the ia afferent neurons to the alpha motor neurons, which activate their own muscle and synergistic muscles. Whenever there is a voluntary contraction, there is coactivation of both alpha (activating the main muscle that is extrafusal muscle fiber) and gamma (activating the spindle muscle that is, intrasfusal fiber) motor neurons. Without this coactivation spindle sensory neurons would be silent during voluntary muscle contraction.
