What is a consequence of demyelination on nerve conduction?

• A. Demyelination slows or blocks conduction along axons
• B. Demyelination increases conduction velocity
• C. Demyelination increases myelin production
• D. Demyelination enhances saltatory conduction

Answer: (A)

When myelin around axons is damaged or lost, the insulation that normally speeds up nerve impulses is compromised. Myelin wraps create long segments with high membrane resistance and low capacitance, so electrical current can travel quickly from one node of Ranvier to the next in a process called saltatory conduction. Demyelination removes that insulation, causing more current to leak out across the membrane between nodes. The depolarizing signal decays before it can reach the next node, so conduction slows dramatically and may even fail entirely along the affected fiber. This loss of fast, reliable conduction explains the slowed or blocked nerve signaling seen in demyelinating conditions.

The other statements don’t fit because demyelination does not increase conduction velocity, does not increase myelin production, and does not enhance saltatory conduction; it disrupts the very mechanism that makes rapid conduction possible.