Which is not a part of lower motor neuron:

Lower motor neurons are motor neurons located in either the anterior grey column, anterior nerve roots or the cranial nerve nuclei of the brainstem and cranial nerves with motor function Lower motor neurons are classified based on the type of muscle fiber they innervate: Alpha motor neurons innervate extrafusal muscle fibers, the most numerous type of muscle fiber and the one involved in muscle contraction. Beta motor neurons innervate intrafusal fibers of muscle spindles with collaterals to extrafusal fibers Gamma motor neurons innervate intrafusal muscle fibers, which together with sensory afferents compose muscle spindles. These are part of the system for sensing proprioception