Final answer:
A smaller diameter axon requires more myelination to compensate for increased resistance when conducting signals at comparable speeds. Myelination provides insulation that facilitates faster action potential conduction by preventing current leakage, particularly evident in saltatory conduction along myelinated axons.
Step-by-step explanation:
To conduct a signal at relatively comparable speeds, a smaller diameter axon needs more myelination, to compensate for the increased resistance as axon size decreases. The correct answer to the student's question is c. Myelination, Increased resistance.
Myelination of the axon acts as an insulator that prevents current from leaving, and thus increases the speed of action potential conduction along the axon. The action potential travels more rapidly in myelinated axons due to saltatory conduction, which is the process of the action potential jumping from one node of Ranvier to the next. This is in contrast to continuous conduction in unmyelinated axons, which is slower.
The larger diameter of an axon, the less resistance to the flow of ions, analogous to a wide river allowing water to flow more easily compared to a narrow creek. Therefore, to maintain conduction speeds in smaller-diameter axons, more myelination is required to counteract the increased resistance.