Nerve axon. Computer artwork of a single axon branching into several terminal boutons (button shapes, lower right). The axon has a protective myelin sheath (cylinders, upper frame). Each nerve cell has a single axon which transmits impulses to other cells. These impulses are transmitted by chemicals known as neurotransmitters. These neurotransmitters are released from the terminal boutons into the junction (synapse) between the nerve cell and another cell. The myelin sheath insulating the axon is made up of specialised Schwann cells and helps to speed the transmission of electrical impulses along the axon.