[not in handout, see intranet]
Human Brain
1012 neurons

 

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Aplysia Brain
2 x 104 neurons

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The human brain has roughly 1012 neurons (a million million) whereas the Aplysia californica nervous system contains only 2 x 104 nerve cells (twenty thousand). Aplysia neurons are clustered together in 5 pairs of ganglia, each ganglion containing roughly 2,000 nerve cells.