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Axons are long, branching structures unique to nerve cells that carry information from neurons to other cells. They are covered by a myelin sheath that insulates electrical signals and is responsible for the whitish color of neural tissue. Interference with signals through axons can cause degenerative neurological disorders.
An axon is a long, branching cellular structure that is unique to nerve cells. Like all animal cells, nerve cells, also known as neurons, are covered by a semipermeable membrane, and it is this membrane that makes up the axons. These structures are responsible for carrying information from nerve cells to all other cells in the body. Interference with signals as they travel through axons has been identified as a cause of some degenerative neurological disorders.
The neuron itself is composed of three basic structures: the cell body, the axon, and numerous branching dendrites. The cell body houses the nucleus and other organelles. Dendrites collect information from other parts of the body and carry it into the neuron. The axon carries electrical impulses from the neuron to all other cells in the body. A fatty sheath covering the entire length of the structure serves to insulate electrical signals from interference. Known as the myelin sheath, this protective coating is composed primarily of fat cells and is responsible for the characteristic whitish color of neural tissue.
The many branches of the structure allow the neuron to enervate multiple cells with a single signal. Each branch is capable of producing thousands of specialized structures, known as synaptic terminals. These interact with other cells through electrical signals or through the release of chemical messengers known as neurotransmitters. Each synaptic terminal contacts a target cell, which can be a nerve cell or a functional cell, such as a muscle fiber or white blood cell. The contact point between an axon and a target cell is known as a synapse.
Neurons send information along axons in the form of electrical impulses. The point where the base of the structure originates from the cell body is known as the axon hillock. It is in this region that the electrical signals are generated. Called an action potential, these electrical impulses transmit information by varying the length and frequency of the signals in a sort of neurological Morse code.
The neuron is able to create the voltage necessary for the action potential by controlling the concentration of various ions, both inside and outside the cell. By channeling positive ions along the length of the axon, the neuron is able to generate short electrical signals to activate the enervated cell or cells at the receiving end of the message.
The myelin sheath is a critical component of this process. By isolating axons from interference, myelin sheaths ensure that neurons are able to transmit information quickly and accurately. Myelin sheath degeneration is associated with the disrupted neuronal communication often seen in patients diagnosed with multiple sclerosis. Similarly, Alzheimer’s disease is thought to be related to the destruction of myelin tissue in certain parts of the brain.
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