The different parts of neurons tell us a lot about how these small cells work of the brain.
Neuronal axons, for example, with their elongated, cable-like shape allow electricity to travel through them, regardless of whether or not they are accompanied by myelin sheaths. The dendrites, in turn, fulfill another function which we will see now.
Dendrites are parts of neurons that They are distributed throughout the body that is, both in the brain and spinal cord and in those that are in the ganglia, internal organs, muscles, etc.
Specifically, the dendrites They are small branches that come out of the cell body (the part of the neuron in which the nucleus of the cell is located). Compared to the axon, dendrites are usually shorter and thinner, so they end closer to the cell body.
Besides, On the surface of the dendrites there are still other types of extensions microscopic. These are small formations called dendritic spines which are, in turn, the places where the dendrites fulfill their main function, as we will see.
Dendritic spines and synapses
Since the time of the famous Spanish neurologist Santiago Ramón y Cajal, it has been known that neurons are relatively independent small bodies, that is, that there is a separation between them. A part of this space that separates neurons from each other is the so-called synaptic spaces which are the points through which these nerve cells pass information through substances called neurotransmitters.
The function of dendrites in general, and dendritic spines in particular, is to act as the main contact point for neurotransmitters that arrive from outside That is, the dendritic spines act as terminals to which the stimuli from the other neuron arrive, sending neurotransmitters through the synaptic space. Thanks to this, it is possible to establish the transmission of nervous impulses that allows the functioning not only of the brain, but of the entire nervous system, given that there are neurons distributed throughout the body.
On the other hand, the potential that the brain has when it comes to adapting to circumstances (for example, learning from experience) is also possible thanks to the work of the dendrites. These are what regulate the possibilities of two nerve cells coming into contact with more or less frequency, so they decide the “route” that nerve impulses take.
Over time, the degree of affinity that the dendrites of one neuron gain with the terminals of another creates a regular communication channel, a fact that affects, even if minimally, the progress of the mental operations that are carried out. Of course, this effect multiplied by the number of synapses in the nervous system is not minimal, and it not only affects the functioning of the brain and the rest of the system, but is, in itself, its basis.
On the surface of dendritic spines there are a series of structures called receptors that They are responsible for capturing certain types of neurotransmitters and activating a specific mechanism In this way, a neurotransmitter such as dopamine will reach a receptor compatible with it and cause it to activate a process in the receiving neuron.
If the axons are responsible for making nerve impulses travel through two points of the nervous system, the dendrites are responsible for capturing the chemical substances that come out from the tip of the axons and whether or not these chemical signals are transformed into electrical impulses although this process can also start in the body of the neuron.
That is It is in the dendrites and the neuronal body where electrical signals are born (also called action potentials) that travel through neurons and end at the tips of the axons, causing this part of the neuron to release chemicals. When adequate amounts of neurotransmitters reach the dendrites, depolarization occurs which is the process that generates nerve impulses.
The dendrites are very sensitive to the slightest variations in the type and amount of neurotransmitters they collect and that means that depending on the chemical substances they detect, they initiate one or another pattern of electrical impulses, or that an electrical signal is not generated directly, if conditions are met.
That means It is not necessary that the dendrites do not collect any neurotransmitter so that they do not produce an electrical impulse ; This can also occur if they capture a certain amount of a specific type of chemical. That is why some psychotropic drugs act on the dendrites of neurons, to prevent them from generating electrical signals as they would if it were not for the effect of this active ingredient.
In short, the molecular traces that lived experiences leave in the dendrites and neuron terminals are the basis of the functioning of the nervous system and its ability to cause its activity to vary dynamically. At the same time, they are a fundamental part of the process of managing memories, which are patterns printed on those molecular fingerprints with which the nerve cell works.
