THE HUMAN BRAIN has often been viewed as an outstanding organ among mammalian
brains and is the most cognitively able. It is endowed with an overdeveloped cerebral
cortex that represents over 80 per cent of brain mass, and purportedly containing
100 billion neurons and 10 times more glial cells.
A neuron is an electrically excitable cell that processes and transmits information
by electrochemical signalling. Unlike other cells, neurons never divide, and neither do they die off to be replaced by new ones. The average human brain has about 100 billion
nerve cells and many of them support and protect the neurons.
Each nerve cell may be connected to up to 10,000 other neurons, passing signals
to each other via as many as 1,000 trillion synaptic connections, equivalent by some
estimates to a computer with a 1 trillion bit per second processor. Estimates of the
human brain’s memory capacity vary wildly from 1 to 1,000 terabytes.
