Aksonien

Aksonien are the elongated projections of neurons that transmit electrical impulses away from the cell body toward other neurons, muscles, or glands. While most neurons have a single axon, its length can vary greatly, from fractions of a millimeter to over a meter in humans. The axon serves as a communication cable, carrying information via action potentials and relaying signals to synaptic terminals.

Structurally, an axon is insulated in many regions by myelin, produced by glial cells (oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system). Myelination increases conduction velocity through saltatory conduction, with gaps known as nodes of Ranvier where the axolemma is exposed. The axon contains a specialized cytoskeleton of microtubules, neurofilaments, and actin filaments that organize organelles and provide structural integrity. At the axon terminal, synapses release neurotransmitters that convey signals to the next cell.

Axonal communication relies on fast logistics known as axoplasmic transport, which moves cargoes such as mitochondria, vesicles, and proteins along microtubules. Anterograde transport carries material from the soma toward the terminal, primarily via kinesin motors, while retrograde transport returns materials to the cell body, largely through dynein motors. Axon diameter, degree of myelination, and the presence of nodes of Ranvier influence conduction velocity.

Developmentally, axons grow from developing neurons and establish synaptic connections guided by molecular cues. In the peripheral nervous system, axons can regenerate after injury to a limited extent, whereas CNS axon regeneration is generally restricted. Clinical relevance includes neuropathies, axonal degeneration, and disorders affecting axonal transport, which can impair neural signaling and function.