University years

How do neurons communicate?

This week there were no major scientific news, or at least nothing that caught my attention, so today I can go on with the story of how I ended up doing a PhD in neuroscience in Germany, so let’s go back at it.

Slightly before starting the second semester on that second year, I had to decide whether I wanted my bachelor to be more focused on the medical biotechnologies or the molecular ones: that choice was not an easy one, but a bit dragged by my friends and favourite classmates who I used to study with, I ended up choosing the Biomolecular Biotechnology path. During this semester we only had four courses, two of which were starting to guide you through the path you chose (and in particular those ones were very specific courses on how to manipulate genetics and biochemistry to use it for research and clinical purposes) but we still had a couple of courses shared by both paths, that were Physiology and Histology and Pharmacology. What totally mesmerised me was finally approaching the physiology and histology of our bodies: all the pieces of the previous courses, all that basic stuff I had to learn, were finally falling into the right space and everything that I had to study so far was starting to make sense into a more concrete and global way.

We started understanding how the morphology of the cells and tissues of the human body was related to their function and how and why this relation was important to its final purpose; how cells can communicate in between each other, all the channels that the cells use to change their electrical characteristics and send signals to the other cells around; how the heart and the blood vessels work and up to the ultimate topic that finally made me make the final decision for my master’s studies: how neurons are able to communicate and make, for example, a muscle contract to perform an action, or how the heart is able to contract by itself without a voluntary action of contraction. As I already mentioned in one of my first posts, I wanted to figure out how electrical and chemical signals in our bodies were actually able to create complex behaviours such as falling in love, talk and so on so forth. At that moment when I finally started studying the physical and biological basis of it, I wanted and needed to know more: I wanted to do a master in Neurobiology.

Since we started to get closer to the subject I decided to work on in my life, I will put on hold for now the other very interesting lectures we had on Pharmacology, that I believe deserve a post by itself, and today for the SRF I will talk about how neurons communicate.

“Science Related Fact” (SRF):

The nervous system is composed of the brain, the spinal cord and a large network of nerves that covers all parts of the body. Neurons are the building blocks of our nervous system and are basically electrical devices. Through neurons, we are able to help different parts of our body communicate and allow our brain to control what is going on. Without neurons we would not know anything that is happening in the outside world and we would not be able to control our body.

As I just mentioned, neurons communicate using electrical signals, but also chemical ones, and the direction of these signals is unidirectional: the motor nerve signals (that allow the brain to control our muscles) travel from the brain to the muscle, while the sensory nerve signals (that tell the brain about what is going on in the outside world, for example when we see something, hear something, smell something and so on) travel from the senses to the brain.

Therefore, when a sensory neuron “sees” or “hear” or “feel” something, this sensory stimulus is converted into an electric signal in a sensory neuron. The electric signal produced by the sensory neuron is now called action potential and is carried along the “sending” cell up to the axon terminal, that is basically the end of a neuron. Since neurons are not directly attached to one another, the electric signal is transformed into a chemical signal at the axon terminal, thanks to neurotransmitters. These molecules are released into the synapse, a tiny gap between the axon terminal and the dendrites, essentially the tips of the “receiving” neuron (see schematic below). The chemical signal is now converted once more into an electric one, due to the opening of channels on the membrane of the neurons that allow for ions to flow, hence generating currents.

“Schematic of the unidirectional movement of an action potential through neurons”. The electric signal that is generated in the “sending” neuron, called action potential, travels along the neuron up to the axon terminal. Here the electric signal is transformed into a chemical signal, thanks to the release of molecules called neurotransmitters in the synapse, a tiny gap between two neurons. The molecules released in the synapse can then stimulate or inhibit the action potential in “receiving” neuron. From khanacademy.org

Depending on the neurotransmitter released from the “sending” neuron, it can either stimulate the “receiving” neuron (by opening channels and allowing for the current to flow) or inhibit it (depressing the flow of currents), making it either more likely or less likely to start an action potential of its own. All these happens with very high precision and is repeated again and again. Moreover, this communication between neurons can be strengthened or weakened by an individual’s activities, such as exercise, stress and drug use.

Of course this is just an extreme simplification of the incredibly complicated and yet not well understood communication between neurons that results in very complex behaviours such as social interactions, memory, feelings and so on. However, what we can definitely establish is that all perceptions, thoughts, and behaviours result from combinations of electric and chemical signals among neurons and consequently communication and coordination among different areas of our nervous system.

3 thoughts on “How do neurons communicate?

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