Cut-away illustration showing the anatomy of a neuron's (nerve cell) axon. Each neuron has one axon, an extension through which information passes outwards to other cells. This exchange of information takes place at a synapse (far right) where vesicles (green) containing neurotransmitters are released from the axon. Part of the cell nucleus (round) is at far left. It holds the cell's genetic material in the form of DNA (deoxyribonucleic acid). Surrounding the nucleus is the endoplasmic reticulum (ER, pink and red). Some parts of the ER are studded with ribosomes (dark dots), sites of active protein synthesis. Vesicles (light purple) leave the rough ER, releasing their protein cargo into the Golgi apparatus (light and dark purple) where the proteins are stored before being re-packaged for transport. Mitochondria (blue) are the sites of energy synthesis within the cell. Microtubules (orange rods) are part of the cell's cytoskeleton.