Types of synapses: neuronal communication

The chemical synapse has other specific characteristics. For example, it shows high plasticity. That is, the synapses that have been more active will transmit information more easily.

For the brain to function correctly, neurons must communicate with each other.. These functional interactions between neurons are called synapses. But how does this interconnection occur? How many types of synapses are there?

Apparently, Two main modalities of synaptic transmission are recognized: the electrical synapse and the chemical synapse. In general, synaptic communication usually occurs between the ending of the axon (the longest part) of the sending nerve cell and the cell body of the receiving neuron.

However, contrary to what we may think, the synapse is not produced by direct contact. Neurons are separated from each other by a small gap: the synaptic or intersynaptic space. The two main types of synapses are explained below.. Both are interneuronal connections, but each type has its own characteristics. Let’s see how each one develops.

Types of synapses: the chemical synapse

At the chemical synapse, information is transmitted through neurotransmitters. That is why it is called chemistry; The neurotransmitters would be responsible for transmitting the message.

Besides, These synapses are not symmetrical, but asymmetrical. This means that they are not produced exactly the same from one neuron to another. They are also unidirectional: the postsynaptic neuron, the one that receives the synapse, cannot transmit information to the presynaptic neuron, the one that sends the synapse.

The chemical synapse has other specific characteristics. For example, shows high plasticity. That is, the synapses that have been more active will transmit information more easily. Thus, this plasticity allows adaptation to changes in the environment. Our nervous system is intelligent and prioritizes the communication of those pathways that we use frequently..

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This type of synapse has the advantage of being able to modulate the transmission of the impulse. But how does he achieve it? This is because it has the ability to vary:

The neurotransmitter. The firing frequency. The intensity of the impulse.

In summary, Chemical transmission between neurons occurs through neurotransmitters that can be modified. Thus, the transmission of the chemical synapse occurs in the following way.

Chemical synapse process

First, the neurotransmitter is synthesized and stored in vesicles.Second, an action potential invades the presynaptic membrane.After, Depolarization of the presynaptic terminal causes the opening of calcium channels voltage-dependent. Following this, a influx of calcium through the channels.This calcium causes vesicles fuse to the presynaptic membrane.With that, The neurotransmitter is released into the synaptic cleft via exocytosis..The neurotransmitter binds to receptors in the postsynaptic membrane. The opening or closing of postsynaptic channels.Then, postsynaptic current causes excitatory or inhibitory postsynaptic potentials that change the excitability of the postsynaptic cell. Finally, a recovery of the vesicular membrane of the plasma membrane.

The electrical synapse

At electrical synapses, information is transmitted through local currents. Furthermore, there is no synaptic delay (time it takes for synaptic connection to occur).

This type of synapses have some opposite characteristics to chemical synapses. So, They are symmetrical, bidirectional and have low plasticity. The latter implies that the information is always transmitted in the same way. Thus, when an action potential occurs in one neuron, it is replicated in the next neuron.

Do these two types of synapses coexist?

It is currently known that electrical synapses and chemical synapses coexist in most organisms and in brain structures. However, we are still learning details of the properties and distribution of these two transmission modalities (1).

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Apparently, Most research efforts have focused on exploring how the chemical synapse works.. Thus, much less is known about electrical synapses. In fact, as we have explained before, it has been thought that electrical synapses were typical of invertebrates and cold-blooded vertebrates. However, a large body of data now indicates that electrical synapses are widely distributed in the mammalian brain (2).

In conclusion, It seems that both synapses, the chemical and the electrical, cooperate and interact widely.. Furthermore, it seems that the speed of the electrical synapse can be combined with the plasticity of chemical transmission, allowing us to make decisions or give different responses to the same stimulus at different times.