The cells in your nervous system are called neurons. Scientists believe there are approximately 90 billion neurons in your brain.
You can also call a neuron a nerve cell, or a cell whose job it is to carry electrochemical messages throughout the nervous system. In the 1880s, neuron was used to mean "the brain and spinal column," or the nervous system itself. Later in the nineteenth century, neuron came to mean "nerve cell with appendages," from the Greek neuro-, "nerve."