Nursing Entrance Exam (NEX) Practice Exam

The myelin sheath plays a crucial role in the functioning of neurons, primarily by increasing the speed at which electrical impulses, or action potentials, travel along the axon. This is due to a process known as saltatory conduction, where the action potential jumps from one node of Ranvier (gaps in the myelin sheath) to another, rather than traveling continuously along the axon.

By insulating the axon, the myelin sheath effectively increases the resistance to the leakage of ions across the neuronal membrane. This insulation not only prevents the premature loss of electrical charge but also enhances the overall efficiency of signal transmission. By facilitating this rapid conduction speed, the myelin sheath ultimately helps in reducing signal delay across long neuronal pathways, allowing for quicker communication between neurons.

In contrast, options related to amplifying signals or merely insulating neurons do not capture the full impact of the myelin sheath on impulse transmission speed. While increasing resistance is a characteristic feature of myelination, the primary physiological effect is to optimize the speed and efficiency of neuronal communication by reducing signal delay.