Q.Why does a nerve impulse in a myelinated fibre travel faster than in an unmyelinated fibre of comparable diameter? Explain the idea of saltatory conduction.

[!TLDR] Myelin insulates the axon except at nodes of Ranvier, so the impulse jumps node-to-node (saltatory conduction) instead of regenerating continuously, which is faster than in an unmyelinated fibre. [!ANSWER] Saltatory conduction = the impulse jumps from node to node in a myelinated fibre because only the nod …

In an unmyelinated fibre the impulse must be regenerated at every successive point along the membrane, since the whole membrane is exposed and carries the necessary ion channels — this point-by-point regeneration takes a finite amount of time at each step, making conduction relatively slow. In a myelinated fibre, the insulating myelin sheath prevents ion movement along most of the axon's length, so the depolarizing current instead spreads passively and very quickly beneath the myelin until it reaches the next exposed node of Ranvier, where a fresh action potential is triggered — the impulse thus appears to 'leap' from node to node, called saltatory conduction. Because full regeneration is only needed at the widely spaced nodes rather than continuously, saltator …

Compare what has to happen at every membrane point (unmyelinated) versus only at the nodes …

Do not say the impulse 'skips' the internodal myelin region entirely without any signal — the depolarizing current does spread passively under the my …