How the Brain Works

It is estimated that there are 100 billion nerve cells (neurons) in the brain. Each neuron has contact with several thousand other nerve cells and forms large networks of cells, where electrical signals are rushed and transmitted with different signal substances between the nerve cells. In addition to the nerve cells, there are at least as many or probably more glial cells. One type of these glial cells are astrocytes. They have numerous and long processes and have contact with small blood vessels (capillaries), nerve cell bodies, connections between nerve cells (synapses), nerve cells’ processes (axons and dendrites), meninges and brain cavities (ventricles). The astrocytes sense everything that happens in the nervous system. In addition, they are connected in large networks through channels, called gap junctions. This means that the astrocytes have their own signalling system.

The microglia cells are another type of glial cell that is part of the brain and nervous system’s defence against foreign substances such as viruses and bacteria as well as various toxins. In the event of damage or disease of the brain, these cells are activated and a neuroinflammation occurs as protection.

The blood vessels in the brain are also special. The smallest blood vessels, the capillaries, contain endothelial cells, which together with the processes of the astrocytes form the blood-brain barrier. It is a protective barrier between the brain and the blood, whose function is to selectively allow substances to enter the brain from the blood. Interestingly, signalling substances in the brain such as glutamate and dopamine are present in the blood, but they cannot pass freely into the brain, where they could disrupt the fine-tuned signalling between the brain’s cells and create chaos.

The oligodendrocytes are glial cells that produce myelin, a fat-rich envelope around the processes of nerve cells. Myelin makes the signalling of nerve cells quick and efficient.

The brain cells work very efficiently and it is not difficult to understand that the brain needs a lot of energy for all functions. The brain actually weighs just over a kilo but needs more than 20% of all blood with its sugar (glucose) and oxygen content at any given moment to cope with all the functions for controlling how we move arms and legs, perceive feeling in the whole body, hear and see, be able to think, concentrate, plan activities, and remember. 

It is important to point out that the brain works as a whole. We know that the brain consists of highly specialized areas. There are areas that are specifically responsible for the ability to move the arms and legs, areas that interpret and analyse sound and light impressions as well as areas that with high precision are responsible for language, learning, and memory. Such functions also require an intact brain with fine-tuned signalling and coherence between nerve cell networks and glial cell networks. We perceive that disturbance or imbalance in any signal system in the brain due to injury or illness reduces the ability of the brain to work efficiently and specifically. As a consequence, the brain will work with less precision.