axon

Definition

Target type: cellularcomponent

The long process of a neuron that conducts nerve impulses, usually away from the cell body to the terminals and varicosities, which are sites of storage and release of neurotransmitter. [GOC:nln, ISBN:0198506732]

The axon, a slender projection of a neuron, is the primary conduit for transmitting electrical signals, known as action potentials, from the neuron's cell body to other neurons, muscles, or glands. Its cellular components are intricately organized to facilitate this transmission and maintain its structural integrity. Here's a detailed description:

- **Axolemma:** This is the plasma membrane that encloses the axon. It's responsible for maintaining the axon's internal environment and regulating the flow of ions across its boundary.
- **Axoplasm:** The cytoplasm of the axon, containing various organelles and molecules essential for its function. It's composed of:
- **Microtubules:** Long, hollow cylinders that provide structural support, guide the transport of vesicles and organelles along the axon, and contribute to its shape.
- **Neurofilaments:** Intermediate filaments that provide structural support and maintain the axon's diameter.
- **Microfilaments (Actin filaments):** Involved in axonal transport and the regulation of the cytoskeleton.
- **Mitochondria:** Powerhouses of the axon, responsible for ATP production, which fuels the energy-demanding processes of nerve impulse transmission.
- **Smooth endoplasmic reticulum:** Involved in lipid and steroid synthesis, calcium storage, and other metabolic processes.
- **Enzymes:** Catalyze various biochemical reactions essential for axonal function.
- **Neurotransmitters:** Chemicals stored in synaptic vesicles that are released at the synapse to communicate with other cells.
- **Myelin Sheath:** A fatty, insulating layer that surrounds most axons, dramatically increasing the speed of nerve impulse transmission. It's formed by glial cells: oligodendrocytes in the central nervous system (CNS) and Schwann cells in the peripheral nervous system (PNS).
- **Nodes of Ranvier:** Gaps in the myelin sheath that allow for the rapid propagation of action potentials through a process called saltatory conduction.
- **Axon Hillock:** The region where the axon originates from the cell body. This is where the action potential is initiated.
- **Axon Terminal (Synaptic Terminal):** The end of the axon where it forms a synapse with another neuron, muscle, or gland. It contains synaptic vesicles filled with neurotransmitters.
- **Synapse:** The junction between the axon terminal of one neuron and the dendrite or cell body of another neuron, or a muscle or gland cell. This is where chemical signaling occurs via the release of neurotransmitters.
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Proteins (105)

Compounds (2,689)