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What are the axons of neurons?

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Neurons are the nerve cells thanks to which we are able to think, feel, make decisions and, even more, to be aware.

However, although the concept of "neuron" is well known even beyond laboratories and university classrooms, the truth is that for understanding what our mental life is like is not enough to know that in our head there are tiny cells that send nerve impulses one by one other You also have to understand that there are different parts of 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 leaves from the center of the neuron and goes to a place far from it. The shape of this small structure gives us clues about what its function is. Basically, the role of axons is to make the electrical signals that travel through neurons go to another place in the body.

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

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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 space synaptic between neurons, which is the point at which these nerve cells communicate with each other, normally through signals Chemicals. That is to say, at the tip of the axons the electrical impulse is usually transformed into a release pattern of chemical particles that reach the other neuron through the synaptic space.

The size of the axons

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

The length of the axons of neurons can vary greatly depending on what their function is. For example, it is common in the gray matter regions of the brain to have 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 fine. 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 in length to be able to reach remote 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 applies to all animals with nerve cells. For example, in some species of invertebrates, such as squid, axons can be up to a millimeter thick, with which it can be seen with the naked eye easily. This is so because the thicker the axon, the faster the electrical impulse travels through it, and in the case of squid this is an important ability to make the siphon through which they expel water work well, since they must contract a large part of muscle tissue at the same time to be able to escape quickly by propulsion to jet.

The formation of nerves

As we have seen, axons are not only found in the brain. Like what happens with neuronal cells, are distributed throughout the body: by internal organs, arms and legs, etc.

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

Myelin sheaths

Many times the axons are not alone, but are accompanied by elements known as myelin sheaths, which adhere to its surface to the point of appearing an inseparable component of the neuron.

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

In fact, thanks to the myelin sheaths, electricity does not advance continuously throughout the axon, but jumps between the points of the axon where there is a separation between the sheaths of myelin, areas called nodules of Ranvier. To understand it better, for the agility with which electricity travels this supposes the same The difference between going up a ramp and going up stairs with two more steps appearing each time above. Something similar to what would be expected occurs if the electrical impulse were teleporting to travel through small sections of the axon, from one node of Ranvier to the next.

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