We have all heard of how neurons communicate with each other via electrical impulses. It is true that some of the synapses are purely electrical, but it is chemical elements that account for most of the communication. These chemical substances are called neurotransmitters.
Neurons can participate in several cognitive functions such as learning, memory and interpretation, thanks to them.
Neuron synapses contain more than ten neurotransmitters. Humans have become wiser about the functions of neurotransmission, which has paved the way for major advances in the design and understanding of the effects of psychoactive substances. The most well-known neurotransmitters are: Serotonin, dopamine, norepinephrine, acetylcholine, glutamate and GABA.
In this article, we will look at the following topics to gain a better understanding of the principles of neurotransmission. First, we will look at the different ways that neurotransmitters affect synapses. Then we look at signal transduction, which is the most common way neurotransmitters work.
Effects of neurotransmitters
The primary function of neurotransmitters is to modulate the synapse between neurons. In this way, the electrical connections become more complex, which offers more possibilities. Many of the functions of the nervous system would collapse if the neurotransmitters did not exist and the neurons behaved like simple wires.
The way neurotransmitters affect neurons is not always the same. Chemical effects affect the synapses in two different ways – including the two types of effects:
- Through ion channels: The possibility of a difference between the inner and outer of the neuron produces electrical impulses. The movement of ions (electrically charged particles) causes the difference to change, and the neuron ignites when it reaches a certain activation point. Some neurotransmitters can connect to ion channels in the neuron’s membrane. When they hook up, the channel opens, allowing the ions to move even more and the neuron becomes activated.
- Through a metabotropic receptor: This is a more complex modulation. Here, the neurotransmitter connects to a receptor in the neuron’s membrane. However, this receptor is not a channel that can open and close. Instead, it produces another substance inside the neuron. Upon contact with the neurotransmitter, the neuron releases a protein inside it, which changes its structure and function. In the next section, we will take a closer look at this type of neurotransmission.
Signal transduction is the process by which the neurotransmitter modulates the functions of the neuron. In this section, we will focus on the functions of the neurotransmitters that do this through a metabotropic receptor, as this is the most common function they have.
The four different phases of signal transduction
- The first messenger or neurotransmitter: First, the neurotransmitter attaches itself to the metabotropic receptor and changes its structure, creating a substance called G-protein. The connection of the receptor to the G-protein induces the release of an enzyme on the inner side of the membrane, creating the detachment of the second messenger.
- The second messenger: The second messenger is the protein that triggers the enzyme that is linked to the G protein. Its mission is to go through the neuron until it finds a kinase or phosphatase. These substances are activated when the other messenger connects himself to one of them.
- The third messenger (kinase or phosphatase): This varies depending on whether the second messenger encounters a kinase or phosphatase. Encountering a kinase activates it and initiates a phosphorylation process in the nucleus of the neuron, causing the neuron’s DNA to begin producing proteins that it did not do before. If the other messenger encounters a phosphatase, it has the opposite effect: It will deactivate the phosphorylation process and stop the production of certain proteins.
- The fourth messenger or phosphoprotein: When the kinase is activated, it sends a phosphoprotein to the neuron’s DNA to activate the phosphorylation. The phosphoprotein activates a transcription factor that will then activate a gene as well as the production of a protein; this protein, depending on its qualities, will elicit several biological responses that end up modifying neuronal transmission. When the phosphatase is activated, it destroys the phosphoprotein, which stops the phosphorylation.
The need for neurotransmitters
Neurotransmitters are incredibly important chemicals in our nervous system. They are responsible for modulating and transmitting information between the different brain cells.
Their effect on neurons can last from seconds to months and even years. Thanks to research, we now understand the connection between many complex, cognitive processes such as learning, memory and attention.