How many synapses does a brain have, and how many does one neuron receive? · Grey Matter

Estimates for the adult human brain range from about 100 to 500 trillion synapses, with about 150 trillion in the neocortex alone, roughly a billion in every cubic millimetre of cortex.

How many synapses does a brain have, and how many does one neuron receive?

Estimates for the adult human brain range from about 100 to 500 trillion synapses, with about 150 trillion in the neocortex alone, roughly a billion in every cubic millimetre of cortex. A cortical or hippocampal pyramidal cell receives thousands to tens of thousands of synapses, most of its excitatory ones on dendritic spines, and the number varies widely by cell type and region. These counts mean that each neuron hears from thousands of others at once, and that the brain's storage lies in the pattern of strengths across these synapses more than in the neurons themselves.