1.The human brain is the largest brain of all vertebrates relative to body size
2.It weighs about 3.3 lbs. (1.5 kilograms)
3.The brain makes up about 2 percent of a human's body weight
4.The cerebrum makes up 85 percent of the brain's weight
5.It contains about 86 billion nerve cells (neurons) — the "gray matter"
6.It contains billions of nerve fibers (axons and dendrites) — the "white matter"
7.These neurons are connected by trillions of connections, or synapses