What is inside your head?

Our head controls our entire body. Cut if off and the result speaks for itself: nothing works anymore…

So, what is inside our head that makes it so vital? Everybody knows that one part of the answer lies in the human brain. But there is much more.

On average, a head weighs between 4.5kg and 5kg, around 7-8% total weigh of a human body. A bigger head doesn’t make you more intelligent; nor does a lighter head. Most skulls have an average weight of 1kg, while your brain is 1.5kg. The rest is made of skin, muscles, water, fat, etc…

The proportion of water is extremely important for your brain: more than 75% of it is made of water. Much more than the rest of your body; water represents “only” around 56% of the overall weight of an adult.  It might seem disturbing but we are mostly made of water. Hence the importance of drinking…

That was for the sizeable part of this article, but the main question remains: what is inside our head?

When you open a head, what can you see? Of course, don’t try it at home, a lot of pictures are available on the Internet. But when surgeons do it, what do they see? On the first sight, just a big pink lump, looking like chewing gum… On the outside, it’s big, it’s pink and its compressed. On the surface, there are a lot of wrinkles and cracks. On the inside, it’s a mix of grey and white matter.

This is the Cerebral Cortex, the outermost sheet of neural tissue, between 2 to 4 millimetres thick. It is divided into two hemispheres,the left and right hemispheres. It contains around 15 to 33 billions of neurons and is formed from six different layers, each of them with a different mix in term of neurons and connections. The Cerebral Cortex plays a central role in memory, language, thought, attention, senses and consciousness.

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Go deeper, and it appears that it is one part of a complex and intricate system called the Nervous System. There are two types of nervous systems: the Central Nervous System (CNS) and the Peripheral Nervous System (PNS). The first one contains the brain and the spinal cord, a pathway for information to be delivered to the brain through nerves spread in all your body, while the PNS is in between the brain and the spinal cord. It allows movement and circulation of information (like spinal cord) but from limbs and organs. The skull does not protect it, damage on the PNS leads to paralysis.

The word “brain” is a misleading word here, and refers to Encephalon; basically standing for “inside the head”.  It means the Brain (as we know it), the Meninges, the Cerebellum (little brain) and the Brainstem. Each of them has a different role: the Meninges envelope and protect the CNS while the Cerebellum plays a major role in motor control and coordination. The Brainstem is a continuation of the spinal cord, providing motor and sensor innervation to the face and neck.

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Even if the brain fills the biggest part of our head, many little pieces come to play, each of them with a role as important as vital. Suffer damage to one of these part, and you will never be as functional as you used to. While the brain deals with most information and chooses out of them, other parts are essential in the functioning of our body.

Nowadays, mysteries in Neuroscience lie in the interconnection of all parts together. Difficulty arises because each part of our brain doesn’t have a definite role: even if the Cerebellum leads our motor control system, it is also involved in cognitive function, such as emotions and language. How is this system functioning when it has to deal with a problem that requires more than one part of our head to work together? More and more is learned about it, but lots is yet to be discovered.

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