Afferent pathway and efferent pathway: the types of nerve fibers

It is natural to associate the concepts "neuron"and" brain ". After all, neurons are the type of cell to which we normally attribute the ability to think, reason and, in general, perform tasks related to the intellect.

However, neurons are also an essential part of the nerves that run throughout our body (along with glial cells). It is not strange, if we take into account the function of these nerve fibers: make certain types of information travel through our organs and cell tissues. Now, although all these data transmission routes do basically the same thing, there are certain nuances and differences between them that make it possible for us to classify them according to their function. That is why we talk about the difference between afferent pathway and the efferent pathway.

Afference and efference: one letter changes everything

To understand the concepts of afferent and efferent, it is very useful to imagine the functioning of the nervous system as cognitive psychologists do, who use the metaphor of the computer as a descriptive model of neural networks

. According to this metaphor, both the brain and the entire nervous system work in a similar way to how a computer does; It has a part of its structure dedicated to being in contact with the environment that surrounds it and another that is dedicated to working with data that it has stored and processed to obtain new information.

Thus, the neurons of the brain and spinal cord would be this "internal" part of the computer, while the nerves that sprout from the spine and reach the most recondite corners of the body are the part in contact with what Exterior.

This last part of the nervous system, called peripheral nervous system, is where the afferent and efferent pathways meet, which are the input and output channels of the central nervous system, respectively.

The pathways through which sensory information travels

Thus, all the information that enters through the sensory neurons travels through the afferent pathways, that is, those that transform the information collected by the senses and transform them into nerve impulses. Instead, efferent pathways are responsible for propagating electrical impulses that are intended to activate (or deactivate) certain glands and muscle groups.

Thus, if we wanted to stick to a simple explanatory scheme about what an afference and an efference are, we would say that the former informs the central nervous system about what happens in the rest of the body and in the data about the environment that it receives, while the efferent neurons are in charge of "transmitting the orders" and initiating the action.

In the same way, the word afference serves to designate the information that travels through these routes of the peripheral nervous system, while the term efference is used to refer to the output (or output) of data that goes from the central nervous system to muscle fibers and glands responsible for releasing all kinds of substances and hormones.

A help to remember better

The distinction between afferent and efferent is very useful to understand how we perceive and act on the environment, but it can also be quite problematic because it is easy to confuse both terms and use them to designate the opposite of what is meant.

Fortunately, using simple memory tricks it is very easy to remember what each thing is, and the The fact that these words are only differentiated by one letter means that remembering one also recalls the other. For example, the "a" of "afferent" can be related to the a of arrival (“Arrival” and English), and the “e” of “efferent” with the first letter of “shipment”.

Pawn neurons?

The afferent and efferent pathways suggest a hierarchical functioning of the nervous system: while some neuronal groups inform about what happens in the rest of the body and transmit orders to implement plans, strategies and action protocols, others carry out the decision-making and give the orders that others will comply with. However, the functioning of our nervous system is not as simple as can be intuited in this vision so schematic of the travels made by nervous information throughout our body, for two reasons basic.

The first is that afferent and efferent neurons do not just passively transmit information: they also cause it to transform. What reaches the spinal cord and the glands and muscles is a burst of data whose shape depends in large part on how it has found each and every one of the neurons for which it has traveled.

The second reason is that, although it is true that decision-making depends more on the brain than on the neural networks of the peripheral nervous system, it is not clear who rules over whom, because they all occupy a place in a data cycle.

After all, the afferent neurons send information to the brain without which action plans cannot be initiated, and the way in which the efferent pathways transmit the information will have an impact on the body and the environment that will then affect the afferent neurons and, therefore, the brain. Consider, for example, the fact of keeping a box of cookies so as not to fall into the temptation to snack between meals: a modification of the environment makes us think and feel differently later than we would with the box of cookies to the sight.

Ultimately, the afferent and efferent neurons may have a simpler and easier task to do. study than that of the nerve cells of the brain, but they still have a vital role in our day a day.