Final answer:
When an action potential encounters a myelin-covered section of a neuron, it moves by saltatory conduction, rapidly 'jumping' from one node of Ranvier to the next, which increases the speed of neural signaling.
Step-by-step explanation:
When a nerve impulse, or action potential, encounters a myelinated section of a neuron, it undergoes a process called saltatory conduction. Myelin acts as an insulator that prevents current from leaking out of the axon, thereby increasing the speed of action potential conduction. In contrast, in unmyelinated neurons, the action potential must propagate along the entire axon membrane, which is a slower process.
The nodes of Ranvier are small gaps in the myelin sheath that contain concentrated voltage-gated Na+ and K+ channels. These nodes are where the action potential is regenerated as it 'jumps' from one node to the next. This allows for rapid conduction along the axon as the impulse moves from node to node instead of spreading continuously and more slowly along the entire membrane.
Moreover, saltatory conduction is also energy efficient since ion channels are only needed at the nodes, reducing the metabolic cost for the neuron. Demyelinating diseases like multiple sclerosis illustrate the importance of myelin as they cause slowed conduction of action potentials due to the loss of insulation on the axon.