muscle spindle anatomy

muscle spindle, muscle spindle, muscle spindles, muscle spindles, intrafusal fibers, Intrafusal muscle fibers, intrafusal muscle fiber, extrafusal muscle fibers, alpha motor neuron, muscle spindle, gamma motor neuron, intrafusal fibers, intrafusal muscle fibers, extrafusal fibers, muscle fiber, muscle fiber, intrafusal muscle fiber, extrafusal muscle fiber, alpha motor neuron, gamma motor neuron,