The Human Brain

The brain is the most complex organ in the human body. It produces our every thought,action, memory,feeling and experience of the world. This jelly-like mass of tissue, weighing around 1.4 kilograms,contains a staggering one hundred billion nerve cells, or neurons. Each neuron can make contact with tens of thousands of others, via tiny structures called synapses. Our brains from a million new connections for every second of our lives. The pattern and strength of the connections is constantly changing & no two brains are alike. It is in these changing connections that memories are stored, habits learned and personalities shaped,by reinforcing certain patterns of brain activity, and losing others.

While people often speak of their 'grey matter' , the brain also contains white matter. The grey matter is the cell bodies of the neurons, while the white matter is the branching network of thread-like tendrils-called dendrites and axons-that spread out from the cell bodies to connect to other neurons. The brain also has another,more numerous type of cell, called glial cells. These out number neurons ten times over. Once thought to be support cells,they are now know to amplify neutral signals and to be as important as neurons in mental calculations. There are many different types of neuron,only one of which is unique to humans and the other great apes,the so-called spindle cells.

Brain structure is formed partially by genes,but largely by experience. Only relatively recently it was discovered that new brain cells are being born throughout our lives-a process called neurogenesis. The brain has bursts of growth and then periods of consolidation, when excess connections are pruned. The most notable bursts are in the first two or three years of life, during puberty, and also a final burst in young adulthood. How a brain ages also depends on genes and lifestyle too. Exercising the brain and giving it the right diet can be just as important as it is for the rest of the body.

The neurons in our brains communicate in a variety of ways. Signals pass between them by the release and capture of neurotransmitter and neuromodulator chemicals. Some neurochemicals work in the synapse,passing specific messages from release sites to collection sites, called receptors. Others also spread their influence more widely, like a radio signal, making whole brain regions more or less sensitive.