Traditional lap pools are about 10 feet wide, though widths between 8 and 10 feet are common. (In competition pools, swim lanes are 2.5 meters wide, or about 8.2 feet.) You don't want to go too narrow with a lap pool.
The number of neurons in the brain varies dramatically from species to species. One estimate (published in 1988) puts the human brain at about 100 billion (10 11) neurons and 100 trillion (10 14) synapses.
The human brain has about one billion neurons. Each neuron is a cell that uses biochemical reactions to receive, process, and transmit information. In simple terms, a neuron is a cell specialized to conduct and generate electrical impulses and to carry information from one part of the brain to another.