What is synaptic space and how does it work?

The nervous system is made up of 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 of which human beings are capable, allowing us to stay alive, run, speak, relate, imagine or to 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 goal. However, these nerve cells are not attached to each other. Between the different neurons that are part of the nervous system we can find a small space through which communication with the following neurons occurs. These spaces are called synaptic spaces.

Synapse 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 20 to 40 nanometers and filling of synaptic fluid that is part of the neuronal synapse, along with pre and postsynaptic neurons. Thus, 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 called 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 a neuron and the dendrites another, called axodendritic synapse, is the most common. In addition, it is possible to find electrical and chemical synapses, the latter being much more frequent and which I will talk about in this article.

The transmission of information

The involvement of the synaptic space, although carried out passively, is essential in the transmission of information. Upon the arrival of an action potential (caused by the depolarization, repolarization and hyperpolarization in the axon cone) at the end of the presynaptic axon the terminal buttons of the neuron are activated, which expel a series of proteins and neurotransmitters, substances that exert chemical communication between neurons that the next neuron will pick up through the dendrites (although in electrical synapses this does not occur).

It is in the synaptic space where neurotransmitters are released and irradiated, and from there they will be captured by the postsynaptic neuron. The neuron that has released the neurotransmitters will reuptake the excess 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 balance of the system (it is in this reuptake process that many psychotropic drugs interfere, such as SSRIs).

Enhancing or inhibiting electrical signals

Once the neurotransmitters are captured, the reactionary postsynaptic neuron in this case the continuation of the nerve signal through the generation of 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 by altering the electrochemical balance.

And is that the synaptic connection between neurons does not always imply the passage of the nerve impulse from one neuron to another, but it can also cause that it does not replicate and is extinguished, depending on the type of connection that is stimulated.

To understand it better, it is necessary to think that not only two neurons are involved in nerve connections, but that We have a great multitude of interrelated circuits that can cause a signal that a circuit has issued. For example, in the event of an injury, the brain sends pain signals to the affected area, but through Another circuit temporarily inhibits the pain sensation to allow the stimulus to escape harmful.

What is the synapse for?

Considering 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 electrochemical impulses that govern the functioning of the body.

In addition, thanks to it, neurotransmitters can remain in the circuit for a time without the need for the neuron to presynaptic is activated, so that although initially they are not captured by the postsynaptic neuron, later it could be done use of them.

In an opposite sense, it also allows surplus neurotransmitter to be re-uploaded 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 the residues generated by nervous activity from the system, which could cause the intoxication of neurons and their death.

Synapses throughout life

The human being as an organism is continuously active throughout the entire life cycle, be it executing an action, feeling, perceiving, thinking, learning... All these actions assume that our nervous system is permanently activated, emitting nerve impulses and transmitting the neurons orders and information from one to another through the synapses.

When a connection is formed, neurons come together thanks to neurotrophic factors that make it easier for them to attract or repel each other, although without ever touching. When connecting, 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 entire life cycle, through the continual creation and pruning of neural connections.

The activity of life and the different actions that we carry out have an effect on synaptic activity: if the activation of a circuit is strengthened, while if it is not exercised in a large amount of time, the connection between neural circuits becomes weakens.

Bibliographic references:

• 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.