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Nodes of Ranvier: Function and Definition Video

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  • 0:00 What are Nodes of Ranvier?
  • 1:15 Function
  • 1:40 Structure
  • 2:45 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb
Neurons make up the brain, spinal cord and nerves that connect to our bodies, and they control all function in our bodies. They are coated in a thick insulation that has small breaks, called nodes of Ranvier. This lesson explains the structure and function of the nodes of Ranvier.

What are the Nodes of Ranvier?

Before we can get a clear definition of the nodes of Ranvier, we should first get a better understanding of what neurons are and how they work. Neurons have three key parts: the dendrites, which receive signals, the cell body, which contains the nucleus, and the axon, which sends signals. The axon is coated in a fatty substance called myelin, which is secreted by cells called oligodendricytes or Schwann cells. Below is a diagram of the parts of a neuron.

Parts of a neuron

Myelin insulates the neuron like plastic insulates electrical wires. Neurons send signals using electricity, so the myelin helps to keep the signal moving quickly over long distances. Think of the coating on wires in your house that prevents the electric current from diffusing out of the wires, and helps to move the current faster. Myelin does the same thing. But, in order for the signal to propagate through the neuron, there must be breaks in the myelin coating.

These breaks are called nodes of Ranvier. Below is a diagram of a support cell, the oligodendricyte, wrapped around the axon, creating the myelin sheath and nodes of Ranvier.

Myelin Sheath

Function

Nodes of Ranvier are the spaces between the myelin coating on the neuron's axon. Much like the plastic coating on a wire needs to be clear to connect to an appliance and supply power, there must be breaks in the myelin to conduct electricity in neurons.

Electricity travels quickly through the axon wrapped in myelin. At the nodes of Ranvier, electricity can be conducted within the cell's environment, and the electrical signal will be propagated down the axon.

Structure

Nodes of Ranvier have space exposed to conduct electricity with the environment to propagate the signal down the axon. At the nodes of Ranvier the cell membrane, or boundary of the cell is exposed. This part of the membrane has proteins, called channel proteins, which allow ions to enter and exit the cell. They're like doors for the cell, letting specific people in and out.

This whole process is largely controlled by sodium and potassium ions. Below is a diagram of the sodium and potassium ion channels in neurons. These channels are in the membrane at the nodes of Ranvier.

neuron channels

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