Action potentials travel the length of the axons of motor neurons to the axon terminals. these motor neurons action potentials travel the length of the axons of motor neurons to the axon terminals. these motor neurons extend from the spinal cord to the sarcolemma of a skeletal muscle fiber arise in the epimysium of a skeletal muscle and extend to individual skeletal muscle fibers extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber extend from the brain to the sarcolemma of a skeletal muscle fiber