What is the synaptic space and how does it work?
AND The nervous system is constituted by an extensive network of nerve connections whose basic component is the neuron . These connections allow the control and management of the different mental processes and behaviors that human beings are capable of, allowing us to stay alive, run, talk, relate, imagine or love.
The nerve connections occur between different neurons or between neurons and internal organs, generating electrochemical impulses that are transmitted between neurons until they reach their target. However, these nerve cells are not hooked to each other. Among the different neurons that are part of the nervous system we can find a small space through which the communication with the following neurons takes place. These spaces are called synaptic spaces .
Synapsis and synaptic space
The synaptic space or synaptic cleft is the small space that exists between the end of one neuron and the beginning of another . It is an extracellular space between 20 to 40 nanometers and filling of synaptic fluid that is part of the neuronal synapse, together with pre and postsynaptic neurons. In this way, it is in this space or synaptic cleft where the transmission of information from one neuron to another occurs , being the neuron that releases the information denominated presynaptic while the one that receives it receives the name of postsynaptic neuron.
There are different types of synapses : it is possible that the synaptic space connects the axons of two neurons between them, or directly the axon of one and the soma of another. However, the type of synapse in which the axon of one neuron and the dendrites of another are communicated, called the axodendritic synapse, is the most common. Likewise, it is possible to find electrical and chemical synapses, the latter being much more frequent and of which I will speak in this article.
The transmission of information
The implication of the synaptic space, although performed passively, is essential in the transmission of information. Before the arrival of an action potential (caused by depolarization, repolarization and hyperpolarization in the axon cone) The terminal buttons of the neuron are activated at the end of the presynaptic axon , which expel to the outside a series of proteins and neurotransmitters, substances that exert a chemical communication between neurons that the next neuron will capture through the dendrites (although in electrical synapses this does not happen).
It is in the synaptic space where the neurotransmitters are released and irradiated, and from there they will be captured by the postsynaptic neuron. The neuron that has emitted the neurotransmitters will recap the surplus neurotransmitter that remains in the synaptic space and that the postsynaptic neuron does not let pass, taking advantage of them in the future and maintaining the equilibrium of the system (it is in this reuptake process that many psychoactive drugs, such as SSRIs, interfere).
Empowering or inhibiting electrical signals
Once the neurotransmitters are captured, the postsynaptic neuron would react in this case the continuation of the nerve signal by generating excitatory or inhibitory potentials, which will allow or not the propagation of the action potential (the electrical impulse) generated in the axon of the presynaptic neuron when altering the electrochemical balance.
And is that the synaptic connection between neurons does not always imply the passage of the nervous impulse from one neuron to another , but it can also produce that it is not replicated and extinguished, depending on the type of connection that is stimulated.
To understand it better we must think that only two neurons are involved in the nervous connections, but we have a great multitude of interrelated circuits that can cause a signal that a circuit has emitted to be inhibited. For example, before an injury, the brain sends pain signals to the affected area, but through another circuit the pain sensation is temporarily inhibited to allow the escape of the injurious stimulus.
What is the synapse for?
Given the process that follows the transmission of information, we can say that the synaptic space has the main function of allowing communication between neurons, regulating the passage of the electrochemical impulses that govern the functioning of the organism .
In addition, thanks to it neurotransmitters can remain for a while in the circuit without the need for the presynaptic neuron to be activated, so that although they are not initially captured by the postsynaptic neuron, they could later be used.
In an opposite sense, it also allows surplus neurotransmitter to be recaptured by the presynaptic neuron, or degraded by different enzymes that can be emitted by the membrane of neurons, such as MAO.
Finally, the synaptic space facilitates the possibility of removing from the system the residues generated by nerve activity, which could cause the poisoning of neurons and their death.
Synapses throughout life
The human being as an organism is continuously active throughout the life cycle, whether it is performing an action, feeling, perceiving, thinking, learning ... All these actions assume that our nervous system is activated permanently , emitting nerve impulses and transmitting neurons orders and information from one to another through the synapses.
At the moment of forming a connection, the neurons come together thanks to neurotrophic factors that make it easier for them to attract or repel each other, although without ever touching each other. When connected, they leave a small intermediate cleft, the synaptic space, thanks to the modulating action of the same neurotrophic factors. The creation of synapses is called synaptogenesis, being especially important in the fetal stage and in early childhood . However, synapses are formed throughout the life cycle, through the continuous creation and pruning of neural connections.
The activity of life itself and the different actions that we carry out have an effect on the synaptic activity: if the activation of a circuit is repeated to a large extent, it is strengthened, whereas if it is not exercised in a large amount of time, the connection between neuronal circuits weakens.
- Bear, M.F .; Connors, B.W. & Paradiso, M.A. (2002). Neuroscience: exploring the brain. Barcelona: Masson.
- Kandel, E.R .; Schwartz, J.H. & Jessell, T.M. (2001). Principles of neuroscience. Fourth edition. McGraw-Hill Interamericana. Madrid.