Nerve cells, or neurons, can range from .004 millimeters to .1 millimeters in diameter. Their length can be anywhere from a fraction of an inch to several feet long, depending on nerve cell type.
Nerve cells can transmit nerve signals to and from the brain at speeds up to 200 miles per hour. An average nerve cell has anywhere from 1,000 to 10,000 synapses that allow the cell to communicate with other nerve cells, glands and muscle cells.
Different types of nerve cells include sensory neurons and motoneurons, among others. Sensory neurons carry messages from the senses to the central nervous system, while motoneurons carry signals from the central nervous system to the muscles.