How many axons are in the average adult human brain?

Question

Once heard there were nine billion but since have heard there were many more but I forget the number.

Answer 1

Don't confuse axons with neurons. There are approximately 100,000,000,000 neurons in the human brain. Most of them are support cells and have nutritive, immunologic and protective functions. The number of axons per cell vary, mostly in the types of cells. For example Purkinje cells have many axons and therefore many more connections. The number of connections are thought to be about 1 trillion. And the processing power is 100 trillion instructions per second.

Answer 2

Ah, nearly all neurons have only one axon. Purkinje cells of the cerebellum have one axon, this axon undergoes extensive branching, as do most axons, but it still has only one axon. (As clearly shown by the early images by Cajal:
http://www.psu.edu/nasa/images/cajal8.jpg)

There are about 100 billion neurons in the brain, and hence there are about 100 billion axons.

Answer 3

10 to the 14 (2,000-5,000 per neuron). Remember, the cell is the neuron, that contains many axons to create synapses.