The nervous system is made up of a vast network of nerve connections, the basic component of which is the neuron. These connections allow the control and management of the various mental processes and behaviors that human beings are capable of, allowing us to stay alive, to run, to speak, to relate, to imagine or to love.
Nerve connections occur between multiple neurons or between neurons and internal organs, generating electrochemical impulses that are transmitted between neurons to reach their target. However, these nerve cells are not related 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 neuron (s) occurs. These spaces are called synaptic spaces.
Synapse and synaptic space
Synaptic space or synaptic fissure is the small space between the end of one neuron and the start of another. It is an extracellular space from 20 to 40 nanometers and filled with synaptic fluid which is part of the neuronal synapse, as well as pre- and postsynaptic neurons. That way it’s in that space or synaptic fissure where the transmission of information from one neuron to another occurs, Being the neuron that releases the so-called presynaptic information while the one that receives it receives the name of postsynaptic neuron.
There are different types of synapses: It is possible for the synaptic space to connect the axons of two neurons to each other, 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 communicate, called an axodendritic synapse, is the most common. Likewise, it is possible to find electrical and chemical synapses, the latter being much more frequent and which I will talk about in this article.
Transmission of information
The involvement of the synaptic space, although carried out 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) at the end of the presynaptic axon the terminal buttons of the neuron are activated, Which expel a series of proteins and neurotransmitters outwards, substances that exert chemical communication between neurons that the next neuron will pick up through the dendrites (Although this does not happen to electrical synapses).
It is in the synaptic space that neurotransmitters are released and irradiated, and from there they will be picked up by the postsynaptic neuron. The neuron that emitted the neurotransmitters will collect the excess neurotransmitter that it remains in the synaptic space and that the postsynaptic neuron does not let it pass, benefiting in the future and maintaining the balance of the system (it is in this process of collection that many psychotropic drugs, such that SSRIs) interfere.
Improvement or inhibition of electrical signals
Once the neurotransmitters are captured, the reactionary postsynaptic neuron in this case the pursuit of the nervous signal by generating excitatory or inhibitory potentials, which will or will not allow the propagation of the action potential (the electrical impulse) generated in the axon of the presynaptic neuron during the modification of the electrochemical balance.
And this is it the synaptic connection between neurons does not always involve the passage of nerve impulses from one neuron to anotherBut it can also prevent it from replicating and stopping, depending on the type of connection it stimulates.
To understand this better, it is important to think that not only are two neurons involved in nerve connections, but that we have a large number of interrelated circuits which can cause the inhibition of a signal emitted by a circuit. For example, in the event of an injury, the brain sends pain signals to the affected area, but through another circuit, the pain sensation is temporarily inhibited to allow the stimulus from the injury to escape.
What is the synapse for?
Given the process that follows the transmission of information, we can say that the main function of the synaptic space is to allow communication between neurons, regulating the passage of electrochemical impulses that govern the functioning of the body.
Moreover, thanks to this, neurotransmitters can stay in the circuit for a period of time without the need to activate the presynaptic neuron, so that although they are not initially picked up by the postsynaptic neuron, they can be used later.
In an opposite direction, it also makes it possible to capture the excess of neurotransmitter by the presynaptic neuron, or degraded by different enzymes which can be emitted by the membrane of neurons, such as MAO.
Finally, the synaptic space facilitates the possibility of removing from the system the waste generated by nervous activity, which could cause neurons intoxication and death.
Synapses throughout life
The human being as an organism is continuously active throughout the life cycle, whether he is performing an action, feeling, perceiving, thinking, learning … All of these actions assume that our nervous system is permanently activated., Emitting nerve impulses and transmitting orders and information from neurons to each other through synapses.
When a connection is formed, neurons come together thanks to neurotrophic factors which allows them to attract or repel each other more easily, even without ever touching each other. When connected, they leave a small intermediate fissure, the synaptic space, thanks to the modulating action of the same neurotrophic factors. The creation of synapses is called synaptogenesis and is especially important in the fetal stage and in infancy.. However, synapses form throughout the life cycle, through the continuous creation and pruning of neural connections.
The activity of life and the different actions that we perform have an effect on the synaptic activity: if the activation of a circuit is widely repeated, it is reinforced, while if it is not exercised for a long time , the connection between neural circuits is weakened.
Bear, MF; Connors, BW and Paradiso, MA (2002). Neuroscience: exploring the brain. Barcelona: Masson.
Kandel, ER; Schwartz, JH and Jessell, TM (2001). Principles of neuroscience. Fourth edition. McGraw-Hill Inter-American. Madrid.