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Unmyelinated and Myelinated Axons

  • Larger diameter axons tend to be image descriptionmyelinated (covered by a myelin sheath), which allows them to conduct action potentials at greater velocities than smaller diameter, image descriptionunmyelinated axons.
An image showing 3 types of axons, Myelinated by Schwann cells, by oligodendrocytes cells and unmyelinated axons
An image showing 3 types of axons, Myelinated by Schwann cells, by oligodendrocytes cells and unmyelinated axons, Myelinated axon is labeled
An image showing 3 types of axons, Myelinated by Schwann cells, by oligodendrocytes cells and unmyelinated axons, Unmyelinated and Myelinated axons are labeled
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An image showing 3 types of axons, Myelinated by Schwann cells, by oligodendrocytes cells and unmyelinated axons, Unmyelinated and Myelinated axons are labeled
An image showing 3 types of axons, Myelinated by Schwann cells, by oligodendrocytes cells and unmyelinated axons, Schwann cells are labeled
An image showing 3 types of axons, Myelinated by Schwann cells, by oligodendrocytes cells and unmyelinated axons, Oligodendrocyte and Schwann cells are labeled
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  • The sheaths consist of a series of myelinated segments, each extending about 1 millimeter along the outer surface of the axon.
  • The segments are separated by small gaps (about 1 micrometer) called image descriptionnodes of Ranvier (enlarged for this illustration).
An image showing the Nodes of Ranvier in myelinated axons
An image showing the Nodes of Ranvier (labeled) in myelinated axons
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  • Schwann cells and oligodendrocytes form image descriptioncoats of myelin by wrapping the axon with concentric layers of their cell membranes, which are mostly lipid.

Learn more about the anatomy of the nervous system with this interactive quiz and labeling exercises guide.

An image showing the Nodes of Ranvier (labeled) in myelinated axons
An image showing the Nodes of Ranvier in myelinated axons, the node and Myelin are labeled
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  • The layer of insulation created by the myelin coat inhibits current loss from the axon by blocking the movement of ions through the axon membrane.
  • Ion channels in myelinated neurons are therefore mostly image descriptionconcentrated in the nodes of Ranvier.
An image showing the ion channels in Unmyelinated and Myelinated Axons
An image showing the ion channels in Unmyelinated and Myelinated Axons, the ions of Nodes of Ranvier are labeled
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  • In comparison, ion channels in unmyelinated neurons occur along the the image descriptionentire length of the axon.
An image showing the ion channels in Unmyelinated and Myelinated Axons, the ions of Nodes of Ranvier are labeled
An image showing the ion channels in Unmyelinated and Myelinated Axons, the ion channels are labeled for both myelinated and unmyelinated axons
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