The Brain in Numbers

Everybody knows what the brain is, although not everybody has realised how complex it is. The results obtained in  a recent study suggest that every person has more connections in their heads than the sum of all the physical networks of the world. Wow! No wonder  the brain is considered the most complex system in the known universe…

This gives the brain amazing capabilities that I will explain in a future post but let’s be more quantitative for now… let’s check out some numbers on brains!

Your brain weights around 1.5 kg which is about 2.3% of your body mass, which isn’t that much… but your brain consumes 20% of your total energy. If the brain is so energy demanding, maybe it is because it is very important? Is the brain doing many things, even if we are not aware? Well, you probably guessed the answer is YES.

More numbers… the brain has about 100 000 million neurones (10^11), and there are about 10^14 connections, i.e. synapses. An easy calculation gives us an average of 1000 connections per neurone. Just to put you under situation, the numbers of stars in the Milky Way is about the same as the number of neurones you have in your head. If you put them all in a straight line you would reach a distance of 400 000 km. Actually, you could reach the moon.

What it is even more amazing is that besides neurones, the brain also contains glial cells... about 30 for each neurone! These aren’t as popular as the neurones, but do their big numbers  mean they are important? In a few words, glial cells take care of neurones, providing structural support, protection and food.

Just to add some more players to the story, you might be interested in knowing that each neurone communicates with its neighbouring neurones by means of the so called action potentials. These signals propagate thanks to complex biochemical molecules called neurotransmitters. At the moment 63 different types of neurotransmitters have been discovered, providing 3 Nobel prices along the way.

It might be reassuring to know that we have so many neurones, since they are the information processing units of our bodies. But you should know that you are born with even more neurones and that from birth to death you are losing them at a rate of about 100 000 neurones per day…. and what’s even worse is that neurones don’t regenerate.

photo credit: NASA’s Marshall Space Flight Center via photopin cc

In any case, what really matters is not the number of neurones, but the quality of their connections. Our brain is plastic, which means that it evolves and new connections are made every time a new skill is acquired. This fundamental fact is illustrated with the famous sentence “neurones that fire together wire together”. So if you practice something a lot, your brain will build strong connections between the neurones that allow you to perform such a task. As you might have noticed, this works pretty well at youth since new skills are harder to learn as you age. In any case, the surviving good connections make an adult brain more efficient, so don’t be afraid to get old. You will be getting wiser and wiser…and more efficient!

Just as a quick remark and as a little bit of extra brain food, you might be interested in knowing that each atom of your brain (and of your body) comes from the explosions of previous stars (Nucleosynthesis). Next time you hear that “we are all made of star dust”, you should take it literally! How this star dust has been able to gather together in such a complex form as the brain is to me one of the biggest mysteries of all times.

photo credit: Rebecca-Lee via photopin cc
photo credit: NASA’s Marshall Space Flight Center via photopin cc