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Name: Wildman Jackson
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I have heard that approximately 1 million brain cells die every day. Is this number correct? I have also heard that there is enough brain cells to last the average human about 120 years. Is the actual number of brain cells known approximately (or how long they will last)?

I'm just trying to pace myself here.... :)

You have heard wrong. Certainly, not that many die daily. We believe that humans have about 100 billion nerve cells (and ten to fifty times more of supporting cells in the brain with them!). We are born with more than that, but many die during our first year of life. We are unsure of whether there is significant change in that number over later life. There is a shrinking of brain mass in old age. But cell numbers stay about the same, as far as is known. This would be a good project for an enterprising young scientist like yourself! When brains change in function, it is not usually due to losing or gaining cells. It is usually due to changes in connections between cells. These are called synapses. Each brain cell in a human brain receives input from 1000s of other cells, and each of these 1000 cells can put 100s of synapses on that 1 cell that it is communicating with. Each cell therefore can have tens of thousands of synapses. It is the weakening and strengthening of these synapses throughout the brain, that changes how the brain functions for the most part. That is our working theory. But the brain is the most complicated object yet encountered (more cells in it that stars in the galaxy!). It will yield more interesting data yet!

Jim Murray

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