Jan 23, 2013 / 5:00 am
I have spent my career studying illnesses affecting the human brain and trying to help people get back to normal life functioning in spite of these conditions.
During all of this time I have never stopped being amazed by this incredible organ about which we still have so much to learn.
Everything we think and do is mediated by the brain. Weighing in at roughly three pounds in the average human being, the brain is the organ of the mind just like the heart is the organ of blood circulation.
It contains about 100 billion neurons or nerve cells and about 100 trillion synapses which are the connections between nerve cells. These cells and connections interact in amazing ways with highly specialized results more impressive than the best computers we have yet to create.
Each neuron exists to transmit information in the form of electrical impulses and the transmission causes the release of chemicals called neurotransmitters, which interact with receptors on nearby nerve cells.
When a receptor is engaged by a neurotransmitter (such as serotonin, norepinephrine, dopamine or glutamate) it sets in motion a cascade of molecular events in the neuron to which it is attached.
Ultimately, these molecular events turn our genes on or off. Of course most of us probably know that genes are the blueprint for every structure in the human body including our brains.
Just like every other cell in the body, each neuron in the brain contains all of our genes. Differences lie in the combination of genes which are activated in any given cell.
We like to think of ourselves as pretty complex – and we are with about 25,000 genes in countless combinations that make us who we are. A fruit fly has about 13,000 and a mouse has roughly the same number of genes as we do.
Differences between species are determined by variations in their genetic codes.
Brain size is another detail that has often impressed scientists and set humans apart from other animals.
Among mammals brain size is related to the size of the animal. This is a fairly consistent relationship in most animals with the exception of human beings. Our brains are much larger than would be expected based on our size – in fact the human brain is about three times larger than expected.
If you consider just the cortex – the convoluted part of the brain that is most obvious – our brain is even more disproportionately large.
Although this sounds impressive, there were once mammals with even larger brains than us. Fossil records show an early hominid species called Boskops man who lived between 30,000 and 10,000 years ago and had a much larger brain than modern humans. It is likely these early beings were much more intelligent than we are with IQs possibly an average of 40 per cent higher than ours.
It is unknown why the Boskops did not survive. It may be there was a high death rate at birth due to the large head size or it could be that greater intelligence did not give a competitive advantage at that time.
Even the often-ridiculed Neanderthal had a larger brain than us.
Regardless, the modern human brain is a marvel and I never tire of learning more of its mystery. It is incredible the advances made in the past couple of decades and I believe the coming years will yield even more amazing discoveries.
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