<prompt> Pudendal nerve supplying motor pa to external sphincter is derived fromL5 - S1 rootsS1 - S2 rootsL2 - L3 rootsS2 - S3 roots  <response>: The striated sphincter is innervated by the pudendal nerve from the S2 - S3 nerve roots. The neurons that innervate the urethral sphincter originate in the cord, in an area termed Onuf;s nucleus. The autonomic nervous system also controls the IUS muscle because it is made of smooth muscle fibers. 