Full Idea
It is estimated by Gierer (1988) that the human cerebral cortex alone contains about 300,000,000,000,000 synaptic junctions.
Clarification
Note that is the numerous junctions. The number of neurons is much smaller
Gist of Idea
A 1988 estimate gave the brain 3 x 10-to-the-14 synaptic junctions
Source
Michael Lockwood (Mind, Brain and the Quantum [1989], p.46)
Book Reference
Lockwood,Michael: 'Mind,Brain and the Quantum:The Compound 'I'' [Blackwell 1991], p.46
A Reaction
As we grasp the vastness of this number, and the fact that the junctions are all active, the idea that a brain does something astonishing is not quite so surprising.