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