Final answer:
The myelin sheath on an axon accelerates all impulses by insulating the axon, leading to faster transmission of nerve signals and increased efficiency compared to unmyelinated axons.
Step-by-step explanation:
The presence of a myelin sheath on an axon tends to accelerate all impulses. Myelin is a lipid layer produced by glial cells, like Schwann cells or oligodendrocytes, depending on whether the axon is in the peripheral nervous system or in the central nervous system (brain and spinal cord), respectively. The myelin sheath acts as an electrical insulator, enabling nerve impulses to jump between the gaps in the sheath, known as the Nodes of Ranvier. This jumping mechanism, called saltatory conduction, allows for more rapid signal transmission along the axon compared to unmyelinated fibers. Diseases such as multiple sclerosis illustrate the importance of the myelin sheath, as the loss of this insulating layer results in significantly slowed and impaired nerve signal transduction, affecting multiple bodily functions.