Axon Definition, History, Structure, Functions, and How It Work – The nervous system in parts of our brain is composed of nerve cells called neurons.
These neurons consist of cell bodies (containing the cell nucleus and organelles) as well as nerve fibers that serve to transmit signals. Between one neuron and another neuron connect and communicate with these nerve fibers. The ability of neurons to transmit signals is also determined by the structure of these fibers.
The constituent structure of nerve cells includes axons, dendrite, cell bodies, Schwann cells and others.
The definition of axon or commonly referred to as neurite is a long-sized neuron fiber that looks like a branch of the body of a cell. Similar to dendrite, but the difference between axons and dendrite is that the number of axons is only one with a larger size and length. Axons are protected by a sheath called a myelin sheath.
Terminal axons are also defined as long, thin cells and axon function keeping potential action away from soma or neuron body cells and ending up in other neurons.
Axons are the main delivery line of the nervous system and provide a help of nerve formation. Individual axon sizes range from 1 μm and the longest axons in the human body are in the sciatic nerve that moves the base of the spine to the large fingers of each foot ranging in length of 1 meter or more.
The function of axons is to deliver stimuli (impulses) from the body of cells to the effectors that are muscle cells and also glandular cells. Axons get help from neurofibrils. In some neurons, axons are protected by myelin membranes.
Generally, the axon tip is connected to the dendrite of other neurons. The location of axons and dendrite meets will form a gap called synapses, where in this synapse there will be an exchange of information between nerve cells.
German neuroanatomist, Otto Friedrich Karl Deiters is generally credited with the discovery of axons, which distinguish this structure from dendrite. Swiss Albert von Kölliker and German Robert Remak were the first to identify and characterize early axon tracking. Kölliker named it axon in 1896.
The axon extends from the body of the cell to the end of the terminal (synapses). Axons look like tails attached to neuronal cells. The larger the axon, the faster the impulse delivery process.
Some axons are covered with a fatty substance called myelin sheath. These shrouded axons are faster in impulse delivery than those not shrouded. Although generally connected with dendrite, axons can also be connected to cell bodies (somas) or even other axons.
The length of the axon can reach one meter. The longest axon in the human body is on the sciatic nerve that extends from the base of the spine to the toe. However, there are some axons that are one millimeter long. The diameter is 1-20 micrometers in mammals. But there are axons in squid that are up to 1 millimeter in diameter.
Axons are different from dendrite. Axons are cylindrical, while dendrites are branched and tapered. Dendrite acts as an impulse receiver while the axon sends it. Axons are much thicker and longer than dendrite.
In the nervous system, axons or neurites have the following functions:
- As the successor to the impulses (stimuli) of the body of nerve cells in the form of potential action
- As an increase in signal transmission through myelin sheath
- Will send impulses to other nerve cells, muscles and glands
- Prevent impulses from breaking out
- It is a calcium ion channel
- As the controller of the target cell to which the impulse is carried.
How Axons Work
At rest, the potential of the axon membrane is about -70 mV. The charge is determined by the ATP pump (Na/K pump) in the membrane.
The pump will ensure that the number of positive ions on the outside of the membrane will be greater than the inside. When depolarization neurons or neuron’s charge positively, so communication will be delivered down electrically controlled neurites where the ion channel opens so that the charge can spread throughout the neurite to the axon terminal which is the place of release of neurotransmitters.
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