Skeletal muscle innervation

Skeletal muscle fibers are innervated by two types of motor neurons, alpha and gamma fibers. This occurs as there are two categories of muscle fibers; those that contract to generate tension (extrafusal fibers), and those that function within muscle spindles to adjust their length during muscle shortening (intrafusal fibers). Muscle spindles are sensory structures within the muscle that allows muscle proprioception (sensing muscle length and changes in length). Additionally, there are sensory fibers associated with muscle spindles, providing that sense of muscle length.