 - - - - - NEURONES AND SYNAPSES |
Look carefully at the two diagrams below:
Firstly, here is a diagram of one of the nerve cells called NEURONES which make up our brain.
Every neurone has a nucleus, with a membrane around it and a series of branches which connect it with the cells around it.
With a bit of imagination, we could see a neurone as a large oak tree. A main trunk with roots, then branches which divide into smaller branches and so on until the top branches almost reach the sky. Similarly, a neurone has up to 10 000 points of contact with the neurones surrounding it.
Each dendrite can measure a few tenths of a millimetre, a few millimetres or even several dozen centimetres, according to the distance from the contact point it must reach.
We have some tens of billions of these neurones in our brain, which means that there are hundreds of thousand billion contact points, called synapses, which maintain communication inside our brain. |
This is a photo of a section of brain tissue. So we have some idea of the incredible complexity of the ramifications that permit communication and therefore intelligence, emotion and memory.
Neurones for a lifetime
| Our entire capital of neurones, which will make our mental functions possible throughout life, is given to us at birth. It does not function immediately because the nerve circuits need to be wrapped in protective covering called myelin, which gives the brain the “grey matter” look when seen from outside. By repeating initial experiences, the baby gradually activates the formation of myelin, which will only be completed at the age of 20. |
These neurones are involved in our activities throughout life. There is no danger of having too few neurones, as had once been supposed. Even though we lose quite a number every day, the total mass required for proper brain function is available for our entire lifetime. With the exception of cell destruction through illness or accident, there are enough to keep our mind going until our last breath. |
A family where they talk to each other
The function of the neurone is to receive, retain and transmit information received mostly via the senses, and this is achieved with electrical impulses.
For communication between neurones to occur, the solution would be for the ends of one neurone to touch other neurones. But nature decreed that nerve ends do not touch. So a system had to be invented to permit information to flow freely through the body, without neurones ever touching. So nature came up with an extraordinary procedure called synapsis (from two Greek words meaning “tie together”).
 A short description of the method used:
The electrical impulse reaches the end of a dendrite, where it causes a chemical reaction creating secretions called neurotransmitters which, once they are received by the opposite dendrite, result in the formation of a further electrical impulse. The electricity produces the chemistry which will in turn produce electricity. From synapse to synapse, information flows throughout our body via some 500 000 billion synapses.
But how are fuelled these billions of cells?
This is the role of blood circulation in the brain.
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