What are the axons of neurons?

We examine one of the main parts of neurons, the wires of the human body.

Neurons are the nerve cells thanks to which we are able to think, feel, make decisions and, moreover, to have consciousness.

However, although the concept of "neuron" is well known even beyond laboratories and university classrooms, the truth is that to understand what our mental life is like, it is not enough to know that in our head there are tiny cells that send nerve impulses to each other. It is also necessary to understand that there are different parts of the neurons, in charge of performing different tasks.. Axons are one of these components.

What is an axon?

A neuronal axon is a kind of sleeve or "arm" that comes from the center of the neuron. from the center of the neuron and goes to a place far away from it.. The shape of this small structure gives us clues as to what its function is. Basically, the role of the axon is to carry the electrical signals that travel through the neurons to another part of the organism.

The axon is, therefore, a kind of conduit through which nerve impulses pass at full speed.It acts as a communication channel between the central part of the neuron (which is called neuronal soma or body of the neuron and is where the nucleus with the DNA is located) and another part of the nervous system to which this electrical stimulus has to reach.

At the end of the axons there is either a part of the nerve fiber that contracts when the electrical signal reaches it, or there is a synaptic space between neurons, which is the point where these nerve cells communicate with each other, normally through chemical signals. That is, at the tip of the axons, the electrical impulse is usually transformed into a pattern of release of chemical particles that reach the other neuron through the synaptic space. reach the other neuron through the synaptic space..

The size of axons

If the human body is characterized by anything, it is by its complexity and by the great variety of parts that work together to make it function well. In the case of neuronal axons, this means that their size depends on the type of neuron they belong to and their location and function. Ultimately, what happens in our nervous system has a decisive impact on our chances of survival, which is why evolution has ensured that our species has many specialized nerve cells of different shapes and configurations.

The length of the axons of neurons can vary greatly depending on their function. For example, it is common that in the gray matter regions of the brain there are neurons with axons shorter than a millimeter, while outside the central nervous system there are several axons that measure more than a span, despite being very thin. In short, in many cases, the axons are so short that the distance between their tip and the body of the neuron is microscopic, and in other cases they can be several centimeters long. can be several centimeters long in order to reach distant areas without to be able to reach distant areas without intermediaries.

As for the thickness of axons in humans, they are usually between one and 20 micrometers (thousandths of a millimeter) in diameter. However, this is not a universal rule that occurs in all animals with nerve cells. For example, in some invertebrate species, such as squid, axons can be as much as one millimeter thick.and can therefore be easily seen with the naked eye. This is because the thicker the axon, the faster the electrical impulse travels through it, and in the case of squids this is an important capacity to make the siphon through which they expel water work well, since they must contract a large part of the Muscle tissue at the same time to be able to escape quickly by jet propulsion.

The formation of the nerves

As we have seen, axons are not only found in the brain. As is the case with neuronal somas, they are distributed throughout the bodyThe axons are found in the internal organs, the arms and legs, and so on.

In fact, a nerve is primarily a bundle of axons which is so thick that we can see it directly without the need of a microscope. When we find a nerve in a piece of flesh, what we are looking at is nothing more and nothing less than many axons grouped together in a bundle, combined with other auxiliary nerve cells.

Myelin sheaths

Often axons are not alone, but are accompanied by elements known as myelin sheaths. are accompanied by elements known as myelin sheaths, which adhere to their surface to the point of appearing to be an inseparable component of the neuron.which adhere to their surface to such an extent that they appear to be an inseparable component of the neuron.

Myelin is a fatty substance that acts in axons in a similar way to a rubber insulator along an electrical wire, although not exactly. In short, the myelin sheaths, which are distributed along the axon creating a shape similar to a string of sausages, separate the inside of the axons from the outside of these, so that the electrical signal is not lost through the walls and travels much faster. The protection they offer is directed both to the neuron itself and to the electrical signal transmitted through it.

In fact, thanks to the myelin sheaths, electricity does not travel continuously along the axon, but jumps between the points of the axon where there is a separation between the myelin sheaths, areas called nodes of Ranvier. To understand it better, for the purposes of the agility with which electricity travels, this is the same difference that there is between going up a ramp and going up stairs, each time appearing two steps higher. It is similar to what would be expected if the electrical impulse were teleporting along small stretches of axon, from one node of Ranvier to the next.