Hello, and welcome again to this course.
As you heard during the introduction video, in this week we will discuss some aspect of the brain and of its relationship with the other organs of our body.
The study of brain and of the nervous system, neuroscience, probably begun in earnest around the beginning of the 19th century, when scientists such as Luigi Galvani discovered the role of electricity in nerves and in 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.
Before going further in our journey we need the consider the brain’s characteristics: what makes it a special organ? How does it work?
In humans, the brain is the third largest organ behind the skin and the liver. When thinking of it, everybody imagines its role in the functions that make us truly ‘us’, such as memory, language, emotions or learning. But not everybody knows that the very same brain is also is also responsible for other functions, that we might regard as automatic, such as regulation of wakefulness of temperature or of 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 an enormous importance for the topics we will discuss in these course. The brainstem, an area that is found in the posterior part to 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 for 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 the new discoveries.
Think about the term we sometimes use as synonym to brain: “gray matter”. What we call grey 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 grey matter is contained in a layer on the outside – the so called cerebral 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 colour, which explains the name given to this component of the brain.
The brain is not made only of neurons, or of white and grey matter:  we can also find the blood vessel that bring nutrients and carry waste products away, as well as components that help maintaining a stable chemical environment, fight inflammation and carrying 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. Glial cells surround neurons , supply nutrients to them, help in fighting infection and removing unwanted substances. Furthermore, about 10% of the brain volume is composed of a clear liquid, the so called cerebrospinal fluid. The cerebrospinal fluid cushions the brain and helps maintaining homeostasis.
Finally, the blood brain barrier is a crucial layer of protection: by permitting the transit only of specific categories of molecules, it acts as a defensive barrier and it and helps in maintaining homeostasis. 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.
Thank you for having watched the first lecture of this course! We hope you enjoyed it, and we’re looking to see you in the next one! Bye!