EM 288 Node of Ranvier

Nodes of Ranvier

Transmission electron microscopy (TEM) of a node of Ranvier of a myelinated nerve.

Nodes of Ranvier are small gaps between Schwann cells that periodically interrupt the myelin sheath. These nodes facilitate saltatory conduction, which allows nerve impulses to “jump” from one node to the next. This significantly increases the speed of electrical impulses along an axon.

• Nerve Fiber (yellow) - longitudinal section of an axon of a nerve cell
  • Synaptic vesicles (orange)
  • Slender mitochondria (red) and endoplasmic reticulum (cyan)
  • Microtubules (blue) - longitudinal arrays
• Schwann Cells (green) - different cells on each side of the node
  • Myelin Sheath (dark green) - forms layers of myelin that encircle the axon
• Node of Ranvier - gaps not covered by the myelin sheath
  • Finger-like processes of neighboring Schwann cells interdigitate at the node
  • Contain clusters of voltage-sensitive sodium and potassium ion channels
• Basal Lamina (purple) - separates the nerve and Schwann cells from the surrounding connective tissue (endoneurium)

Courtesy of Keith R. Porter and Mary A. Bonneville, Department of Biology, Harvard University, Cambridge, MA.