Brain
A human brain accounts for about 2% of the body's weight, but it uses about 20% of its energy. It has about 50–100 billion nerve cells (also called neurons), and roughly the same number of support cells, called glia. The job of neurons is to receive and send information to and from the rest of the body, while glia provide nutrients and guide blood flow to the neurons, allowing them to do their job. Each nerve cell has contact with as many as 10,000 other nerve cells through connections called synapses.