Synaptic boutons, also called terminal axons or synaptic bulbsare divisions of the extreme part of the axon that form synapses with other neurons or with muscle cells or glands.
Neurotransmitters are stored in these bulbs, that is, the biomolecules responsible for transmitting information from a neuron to another cell type (be it a target tissue of another biological nature or another neuron).
Recent studies have calculated that the human brain contains 86 billion neurons, an astronomical figure inconceivable to anyone. Therefore, it is not surprising that this cellular network is the cause of our thinking, relationship with the environment, emotions and any characteristic that defines us as “autonomous entities”.
It is for these reasons that knowing the nervous processes in our body becomes essential. Synaptic buttons are vital structures for the exchange of information between neurons.and therefore, in this space we tell you everything you need to know about them.
We cannot embark on investigating paths as complex as synaptic bulbs without first defining where they are located, what they produce and what their relationship is with the surrounding cells. Go for it.
About the neuron
The neuron is a cell type like any othersince it has its own nucleus, is delimited from the rest of the environment and is capable of nourishing itself, growing and differentiating (among many other qualities).
What makes this structure a distinctive unit is its specialization, since Its function is to receive, process and transmit information through chemical and electrical signals.. Quickly, we can distinguish three main parts in the morphology of the neuron:
Synaptic boutons are located at the distal end of the neuron, that is, at the end of the axons. The next part of understanding these complex structures is discovering that they store neurotransmitters, but what exactly are these molecules?
As we have said previously, neurotransmitters are organic molecules that allow the transmission of information from a neuron to another cell body. Various bibliographic sources state that for a neurotransmitter to be considered such, it must meet certain characteristics.. We list them for you:
Neurotransmitters, as foreign as they may seem to the general population, They are nothing more than organic compounds like all those that make up living structures.. For example, acetylcholine, one of the most famous, is composed of carbon, oxygen, hydrogen and nitrogen.
It should be noted that these biological compounds are very similar to hormones, but they have one essential characteristic that differentiates them: hormones generate responses in target cells no matter how far away they are, as they circulate through the bloodstream. On the other hand, neurotransmitters only communicate with the immediate neuron through the synapse.
There is a considerable variety of neurotransmitters, among which are acetylcholine, dopamine, norepinephrine, serotonin, glycine and glutamate. Each one has a special composition and function. For example, serotonin (90% of which is stored in the gastrointestinal tract and blood platelets) is an essential neuromodulator in mood, anger, memory, sexuality, and attention. Who would have thought that a small biomolecule would encode our daily behavior in such a way?
We’ve understood where synaptic buttons are and what they store, but a new term has just come into play: the synapse. We have no choice but to address this process in the following lines.
About the synapse
Neurons communicate with each other through a process called synapses.. This can be electrical or chemical in nature, depending on the method of transmitting information.
At electrical synapses, information is transmitted by an exchange of ions between closely adhered cells. Neurotransmitters do not play an essential role here, since the nervous impulse is transmitted directly from one cell to another through the exchange of these ionic molecules. It is a “more basic” communication, present mostly in vertebrates that are less complex than mammals.
Besides, Chemical synapses are those that use the previously mentioned neurotransmitters to transmit information from a neuron to the target cell. (be it a neuron or another type of cell body). To simplify things, we will limit ourselves to saying that the arrival of the nervous impulse throughout the cell body to the synaptic buttons promotes the release of the neurotransmitters stored there.
These biomolecules are stored in vesicles or “bubbles”. When the excitation signal reaches these bulbs, the vesicles fuse with the bulb membrane, allowing the release of stored neurotransmitters through a process called “exocytosis.”
Thus, neurotransmitters are released into the synaptic space, that is, the physical distance between the two neurons that are transmitting information, and then adhere to the membrane of the postsynaptic neuron, that is, the information receptor that will be responsible for transmitting the new impulse to another cellular target, and so on.
Although it may seem like a merely microscopic and metabolic world, all these small biomolecules and electrical impulses are responsible for the biological calculations that translate, in a behavioral field, into processes as essential as the perception of the environment and human thinking. Fascinating, right?
Essential endings of the neuron
Thus, as we have dissected in each of the previous sections, Synaptic boutons are neuron axon endings that store neurotransmitters. and they release them into the environment so that synapsis can take place, that is, communication between neurons or between a neuron and another target cell.
Various studies try to understand the effectiveness and nature of these synaptic bulbs. For example, in rodents it has been observed that there are a small number of thalamo-cortical buttons, but these have a very efficient synapse due to their structural composition.
We must take into account that cell bodies show variations depending on their area of action and their function. For example, these investigations highlight that The buttons can present morphological diversity in terms of size, number, presence of mitochondria and number of vesicles. (which we remember store neurotransmitters) present refers to. All this, presumably, determines the efficiency and speed of the transmission of the nervous signal.
Other studies show us clear examples of the functionality of these buttons in specific processes and diseases, for example, in neuromuscular junctions. For example, the terminal buttons of these neurons present vesicles with about 10,000 acetylcholine molecules, which when released and received by the muscle tissue cells provoke a response in the individual’s muscles.
Conclusions
As we have seen, synaptic buttons are one more piece of the puzzle to understand the relationship and communication between the components of our nervous system. Neurotransmitters are stored in them, the biomolecules responsible for transmitting information between the pre-synaptic cell and the postsynaptic cell..
Without this communication at the microscopic and cellular level, life as we understand it would not be possible. For example, for a finger to receive the signal to move in front of the fire, this stimulus must be received by the brain, and without communication between each of the components of our body, this signal would never arrive. For all these reasons, we could say that the synapse is the response mechanism that allows life as we know it today in animals.
