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muscle spindle
muscle spindle A muscle spindle is a sensory structure in skeletal muscle made of intrafusal fibers that run alongside the main muscle fibers.
A muscle spindle is a sensory structure in skeletal muscle made of intrafusal fibers that run alongside the main muscle fibers. When the muscle is stretched, it signals the spinal cord and helps trigger a reflex contraction that opposes further stretch, supporting normal muscle tone and indicating muscle length rather than muscle tension.