<prompt> The number of muscle fibers innervated by a motor axon is smallest inGastrocnemiusOrbicularis oculiSingle unit smooth muscleSoleus  <response>: The extraocular and hand muscles have an innervations ratio of 3 to 6 whereas gastrocnemius and back muscle has a ratio of 2000.Refer Medical Physiology by Guyton Hall, 12th edition, page no: 96 