where are voltage gated sodium channels concentrated in myelinated axons
Node of Ranvier An action potential is a spike of both positive and negative ionic discharge that travels along the membrane of a cell.[14] The creation and conduction of action potentials represents a fundamental means of communication in the nervous system. Action potentials represent rapid reversals in voltage across the plasma membrane of axons. These rapid reversals are mediated by voltage-gated ion channels found in the plasma membrane. The action potential travels from one location in the cell to another, but ion flow across the membrane occurs only at the nodes of Ranvier. As a result, the action potential signal jumps along the axon, from node to node, rather than propagating smoothly, as they do in axons that lack a myelin sheath. The clustering of voltage-gated sodium and potassium ion channels at the nodes permits this behavior.
Central nervous system This differentiates the central nervous system from the peripheral nervous system, which consists of neurons, axons and Schwann cells. Oligodendrocytes and Schwann cells have similar functions in the central and peripheral nervous system respectively. Both act to add myelin sheaths to the axons, which acts as a form of insulation allowing for better and faster proliferation of electrical signals along the nerves. Axons in the central nervous system are often very short (barely a few millimeters) and do not need the same degree of isolation as peripheral nerves do. Some peripheral nerves can be over 1m in length, such as the nerves to the big toe. To ensure signals move at sufficient speed, myelination is needed.