 Dear students, in this topic we shall discuss the myelination of axons and the saltatory conduction through these myelinated axons. The vertebrate axons have a thick multi-layered membranous structure around their axons. This structure is known as myelinsheath. Myelinsheath is composed of a fatty substance which is known as syfingo myelins. The myelinsheath is deposited around the axon during the course of development. Two types of specialized glial cells produce this myelinsheath. In the central nervous system, oligodendrocytes deposit myelinsheath, while in the peripheral nervous system, Schwann cells secret myelinsheath around the axons. Dear students, myelinsheath is not a continuous structure. In fact, after 1-3 mm length, small gaps are present. These gaps are known as nodes of renvier. Each node of renvier is approximately 2 to 10 micrometers long. In between, the nodes of renvier are the myelinated areas which are called myelinsheath and these areas are called inter-nodes. Dear students, the nodes of renvier are the places where the extra cellular fluids are directly connected to the membranes. And these are the places where the voltage-gated ion channels are also present. This is because the ion exchange is through the nodes of renvier. Dear students, myelinsheath performs four major functions. First, it provides electrical insulation. Secondly, it increases the speed of conduction. Thirdly, it provides space efficiency. And fourthly, it provides the mechanism of saltatory conduction. We shall discuss these functions in detail. First, we shall discuss the electrical insulation provided by myelinsheath. As the sheath mainly contains the lipid substance sphingomyline, that is actually a poor conductor of electric current. So, this substance provides electric insulation to the egg zone just as electric wires are insulated around the copper wires. It decreases ion flow loss up to 5,000 volts. Second function of myelinsheath is to increase the speed of conduction. Insulation with myelin provides the efficiency of longitudinal spread of current. Due to this, traveling the current in the shape of a long wire increases its efficiency. The result is that the nerve impulse is transmitted at a higher speed. This speed increase is, due to myelinsheath, is much more as compared to increasing the diameter of the egg zone. To increase the length constant of the egg zones, the mechanism in invertebrates, in which the diameter of the egg zone was increased, provides much more speed compared to myelinsheath. For example, if we look at a vertebrate's myelinated egg zone, which is only 20 micrometre thin, the speed of conduction of nerve impulse is more than 800 micrometre thick joint squared egg zone. The third function of myelinsheath is to provide space efficiency because the myelinated fibers can be packed into a space that occupies... Thousands of egg zones can be packed into the space that is taken by one egg zone of squared. This means that the space efficiency provides myelination. The fourth major function of the egg zone myelination is the saltatory conduction. Because ions cannot flow through the myelinated regions of the egg zone, that is, inter-nodes, that is why action potentials are not generated at these inter-nodes. Ions flow only through the nodes of the envir. The inward sodium current produced on the nodes goes to the next node while traveling. In this way, the membrane depolarization and the repolarization are only at nodes of envir. The result is that the action potential that jumps from one node to the other node. This mechanism of conduction of jumping pattern is called saltatory conduction. Because of saltatory conduction, the velocity of nerve transmission increases from 5 to 50 volts. Because of this, the energy consumption or the savings in energy consumption is about 100 times.