Final answer:
A myelinated fiber conducts impulses faster due to the insulating properties of myelin, which enables saltatory conduction along the axon, increasing the speed and efficiency of electrical signal transmission.
Step-by-step explanation:
A myelinated fiber conducts impulses faster than an unmyelinated fiber because the myelin sheath provides insulation that prevents current from leaking out of the axon. This allows the electrical impulses to travel via a process known as saltatory conduction, where the action potential 'jumps' from one node of Ranvier to the next, instead of moving down the entire length of the axon membrane. This insulated conduction method increases the speed of action potential propagation along the axon and reduces the amount of energy consumed.
Furthermore, myelin reduces the capacitance of the axonal membrane, which allows for a more rapid change in voltage. As a result, signal transmission in myelinated neurons is not only faster but also more energy-efficient, limiting cross talk between adjacent nerves and enhancing the fidelity of electrical signal propagation.