In a study of a toddler with delayed motor response, scientists detect a gene mutation that affects the efferent or motor neurons that carry impulses away from the central nervous system (CNS). Scientists discover that this mutation has caused gaps between the nodes of Ranvier and the myelin sheaths of the axons. Explain how this defect in axon structure may have caused a delay of motor response in the toddler?Give an example of a disease that causes a defect in axon structure.