A nerve fiber in the peripheral nervous system that conducts impulses away from the cell body. Axons are covered by a myelin sheath and neurilemma, which is a membranous sheath that covers the axon directly or covers the myelin sheath when it is present. The myelin sheath increases the speed of the nerve impulse conduction and insulates and maintains the axon. The neurilemma assists in the regeneration of injured axons. Axon endings are the terminal portions of the axons. Axon terminals are the endings of the nerve.