Ranvier’s nodules: what they are and how they serve neurons

Ranvier’s nodes are cellular substructures that are part of a neural system. Among other things, they are responsible for the regulation of electrical signals between neurons, that is, they play a very important role in maintaining the activity of the nervous system.

In this article we will see what the nodules of Ranvier are, What are their main functions and what pathologies of the nervous system have been associated with them.

    What are Ranvier’s Nodules?

    Ranvier’s nodules, or Ranvier’s nodes, are small openings that are sandwiched between the myelin sheaths that they cover neural axons.

    To explain it better, let’s go hand in hand: among other things, the vertebrate nervous system is made up of long propagations of neurons that connect to each other. These propagations are called “axons”, originate from the soma (body) of the neuron and are shaped like a cone that stretches as it stretches through the neural network.

    In turn, axons are covered with a thick layer of fat and protein called “myelin”. This thick layer has the shape of a sheath whose function is stimulate the transmission of nerve impulses between neurons. Myelin protects the neural network; it serves as an insulator that accelerates nerve transmission between axons.

    These sheaths or layers of myelin are not uniform or completely smooth, but are made up of small depressions or furrows interspersed along the axon, which we call nodules or nodes. The first to describe both myelin and its nodes was the French physician and histologist Louis-Antoine Ranvier in 1878. This is why to this day these collapses are known as Ranvier’s nodules or nodes.

      What are its functions?

      Ranvier’s nodes are essential for maintaining the function of myelinated axons. These are plots of a very short length which they allow contact between the axon and the extracellular spaceAnd with this, they allow the entry of electrolytes of sodium, potassium and other chemical elements.

      Generally speaking, Ranvier’s nodes facilitate the expansion of electrical impulses to what we call “action potentials” and maintain the electrical activity that passes through axons at an appropriate rate until it stops. ‘they reach the body of the neuron.

      Being a kind of grooves interspersed in the axon, the nodules of Ranvier they allow electrical activity to pass in the form of small jumps between nodes until it reaches the neural nucleus. The latter accelerates the speed of communication between neurons, i.e. the synapse, thus allowing all activity associated with the brain to take place.

      Other characteristics of nodes

      It is now known that small changes in the functioning of Ranvier nodules can lead to large changes in the action potentials, and with it, in the activity of the nervous system. The latter has been particularly linked to the elements that make up the nodes.

      Ranvier’s nodes are made up of channels that allow the passage of substances necessary to maintain electrical activity, in particular potassium and sodium. In these channels, the total voltage variation of the action potentials in the membrane is felt. This is why the nodes of Ranvier are areas with high protein content.

      It is necessary that there be a sufficient number of channels to avoid breakdowns in the propagation of electric current. That is, a significant amount of channels is needed to ensure rapid activation of channels and, with it, action potentials.

      Diseases and related medical conditions

      In order for these nodes to form and function properly, a series of rather complex interactions must take place between the axon and the cells that line it.

      The complexity of these interactions between the nodes and the surrounding regions means that there is the possibility of developing pathologies of the nervous system associated with the functioning of the nodes and more specifically, related to the functioning of the channels that allow the entry of substances and the communication. electric.

      Among other things, these pathologies have the common characteristic that a demyelination process occurs (the damage that occurs in the myelin layers that cover the axons). demyelination causes a significant change in electrical activity, Reduce the speed of momentum and response, and in some cases even causes them to get lost. The consequence is a disorganization of the nervous system.

      The conditions associated with the functioning of Ranvier nodules are very diverse and are still under investigation. They range from autism spectrum disorder, various epilepsy syndromes and fibromyalgia, to autoimmune disorders such as Guillain-Barré syndrome.

      Bibliographical references:

      • Arancibia-Carcamo, L. and Attwell, D. (2014). Ranvier’s node in CNS pathology. Acta Neuropathologica, 128 (2): 161-175.

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