Nodules Of Ranvier: What They Are And How They Serve Neurons
The nodes of Ranvier are cellular substructures that are part of the neuronal system. Among other things, they are responsible for regulating electrical signals between neurons, that is, they are a very important part of maintaining the activity of the nervous system.
In this article We will see what Ranvier’s nodes are what are their main functions and what pathologies of the nervous system have been associated with them.
The nodes of Ranvier, or nodes of Ranvier, are small openings that are sandwiched between the myelin sheaths that cover neuronal axons
To explain it better, let’s go in parts: among other things, the nervous system of vertebrates is made up of long propagations of neurons that connect to each other. These spreads are called “axons,” they arise from the soma (the body) of the neuron and are shaped like a cone that elongates as it spreads through the neural network.
In turn, axons are covered by a thick layer of fatty substances and proteins called “myelin.” This thick layer has the shape of a sheath whose function is stimulate the transmission of nerve impulses between neurons What myelin does is protect the neural network; It serves as an insulator that speeds up nerve transmission between axons.
These myelin sheaths or layers are not uniform or completely smooth, but are composed of small depressions or grooves interspersed along the axon, which we call nodules or nodes. The first to describe both myelin and its nodes was the French doctor and histologist Louis-Antoine Ranvier in 1878. That is why to this day, these depressions are known as nodules or nodes of Ranvier.
The nodes of Ranvier are essential for maintaining the function of myelinated axons. They are plots of very small length that allow contact between the axon and the extracellular space and with this, they make possible the entry of electrolytes of sodium, potassium, and other chemical elements.
Broadly speaking, the nodes of Ranvier facilitate the expansion of electrical impulses that we call “action potential” and allow the electrical activity that passes through the axons to be maintained at an adequate speed until it reaches the body of the brain. neuron.
Being a type of grooves that are interspersed in the axon, the nodes of Ranvier They allow electrical activity to move in small jumps between node and node until reaching the neuronal nucleus. The latter accelerates the speed of communication between neurons, that is, the synapse, which makes it possible for all the activity associated with the brain to take place.
Other node characteristics
It is currently known that small changes in the functioning of the nodes of Ranvier can cause large modifications in action potentials, and with this, in the activity of the nervous system. The latter has been especially related to the elements that make up the nodes.
The nodes of Ranvier are composed of channels that allow the passage of substances necessary to maintain electrical activity, especially potassium and sodium. In these channels the total voltage change in action potentials in the membrane is experienced. This is why Ranvier’s nodes are areas highly populated with protein material
It is a necessary condition that there be a sufficient number of channels to avoid failures in the propagation of the electric current. That is to say, a significant number of channels is necessary to ensure the rapid activation of the channels, and with this, the action potentials.
Diseases and related medical conditions
For these nodes to form and function correctly, a series of quite complex interactions must occur between the axon and the cells that cover it.
The complexity of these interactions between the nodes and the regions that are around them 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 electrical communication.
Among other things, these pathologies have the common characteristic that a demyelination process occurs (damage that occurs in the myelin layers that cover the axons). Demyelination causes electrical activity to change significantly, reducing the speed of impulse and response, and in some cases causing them to even be lost. The consequence is a disorganization of the nervous system.
The conditions to which the functioning of the nodes of Ranvier have been associated are very diverse and continue to be studied. They have been linked to everything from Autism Spectrum Disorder, different Epilepsy Syndromes and fibromyalgia, to autoimmune disorders such as Guillain-Barré Syndrome.
