Introduction to the brain

Hello and welcome again to this course. As you heard during the introduction video, in this week we discuss some aspects of the brain and of its relationship with the other organs of our body. The study of brain and nervous system, neuroscience, probably began when scientists such as Luigi. Galvani discovered the role of electricity in nerves and muscle contractions. Since then, and especially in the last 100 years neuroscience has progressed immensely, and in doing so it has also become an incredibly sexy subject.

We can find articles that describe our brain in love, we can admire works of art that represent the brain and of course we can watch TV series and movies that contain references to the brain the mind and neurosciences. When thinking of the brain you will probably imagine its role in the functions that make us truly human, such as memory, language, emotions, or learning, but not everybody knows that the very same brain is also responsible for other functions that we might regard as automatic, such as regulation of wakefulness, temperature or feeding behaviour.

Many of these functions are regulated by the hypothalamus, a tiny area of the brain about the size of a pea that links the nervous system to the endocrine system and therefore has enormous importance for the topics we will discuss in this course. The brainstem, an area that is found in the posterior part of the brain and that is continuous with the spinal cord also contains areas that regulate vital functions such as the heart and breathing rate and controlling the sleep-wakefulness cycle I am talking about the brain since about a minute, And I already said the word area twice. What are these brain areas? Do they work alone or are they connected in a network?

The latter question is quite important and has been debated for at least two centuries with the mainstream theory changing multiple times in the light of new discoveries. To explain it we can start by thinking about

the term we sometimes use a synonym for brain: Grey matter. What we call gray matter are actually areas packed with the cellular bodies of the neurons, the part of the cell that contains the biochemical machinery and the cell nucleus. Most of the gray matter is contained in an external layer, the so called cerebal cortex, and in nuclei buried inside the brain. The rest of the brain matter is mostly composed of the white matter composed of bundles of axons that connect distant neurons. The axon is a thin filament that starts from the neuron body. We can imagine it just like an electrical cable transmitting electrical pulses.

Just like cables, axons can have an insulating layer unlike cables it is not made of rubber but rather of myelin. Myelin is a fatty substance and it’s whitish in color, which explains the name given to this component of the brain. So, going back to the question, the brain is composed of gray matter areas that are connected by a network of cables if you wish. While the map of the brain and its areas is well defined the link between area and function is not always crystal clear. For many functions indeed we found the link with a network of areas and not with a single region of the brain.

Anyways, the brain is not made only of neurons or of white and gray matter. We can also find blood vessels as well as components that help maintain a stable chemical environment, fight inflammation and carry out useful tasks that are not directly related to our cognitive functions. In particular, keeping a stable environment. In other words, homeostasis, is crucial for the functioning of the brain. This task is not assigned to neurons but to other cells and structures. For instance, about 10 percent of the brain volume is composed of a clear liquid, the so called cerebro-spinal fluid. The cerebrospinal fluid cushions the brain and it is an element that helps in maintaining homeostasis.

Another very important element that both protects the brain and contributes to keeping homeostasis is the blood-brain barrier. It permits the transit only to specific categories of molecules and it acts as a defensive barrier against pathogen and toxins. The blood-brain barrier is one of the reasons why some drugs and molecules are active on the brain and others are not, and we will describe it in more detail in the next article. This concludes this part of our introduction to the brain. We hope you enjoyed this video and we are looking to see you in the next one