Neurons (also known as neuronal cells or nerve cells) are the major components of the brain, spinal cord, and the peripheral nervous system. They are morphologically and functionally diverse; cell bodies can range from 4 to 100 micrometers in diameter and differ in the production of neurotransmitters. Some well-known neuronal markers include NeuN, a nuclear antigen, and PGP9.5, a deubiquitinating enzyme. Other markers include: TUBB3, NSE, HuC, tyrosine hydroxylase, nestin, calretinin, and choline acetyltransferase. Note that new findings may emerge, implicating expression of these antibody markers in other cell types.