Neuroscience

First step to induce self-repair in the central nervous system

Damaged peripheral nerves can regenerate after an injury, for example, following a forearm fracture. Axons, the long projections of neurons that transmit stimuli or signals to other cells, are affected in the case of injury ...

Medical research

Connecting neurons in the brain

The brain consists of a large collection of interconnected neurons. How complex patterns of neuronal cells grow into functioning circuits during development has fascinated researchers for decades. A team of scientists at ...

Neuroscience

Growing a cerebral tract in a microscale brain model

An international research team led by The University of Tokyo modeled the growth of cerebral tracts. Using neurons derived from stem cells, they grew cortical-like spheroids. In a microdevice, the spheroids extended bundles ...

Neuroscience

Perilous ruptures described in a multiple sclerosis model

The permanent neurological deficits of multiple sclerosis patients largely depend on the extent of degeneration of long nerve fibers. The latter is initiated by ruptures in the cell membrane and the resulting influx of calcium ...

Genetics

Gene therapy blocks peripheral nerve damage in mice

Nerve axons serve as the wiring of the nervous system, sending electrical signals that control movement and sense of touch. When axons are damaged, whether by injury or as a side effect of certain drugs, a program is triggered ...

Genetics

New method for studying ALS more effectively

The neurodegenerative disease ALS causes motor neuron death and paralysis. However, long before the cells die, they lose contact with muscles as their axons atrophy. Researchers at Karolinska Institutet in Sweden have now ...

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Axon

An axon or nerve fiber is a long, slender projection of a nerve cell, or neuron, that conducts electrical impulses away from the neuron's cell body or soma.

An axon is one of two types of protoplasmic protrusions that extrude from the cell body of a neuron, the other type being dendrites. Axons are distinguished from dendrites by several features, including shape (dendrites often taper while axons usually maintain a constant radius), length (dendrites are restricted to a small region around the cell body while axons can be much longer), and function (dendrites usually receive signals while axons usually transmit them). All of these rules have exceptions, however.

Some types of neurons have no axon—these are called amacrine cells, and transmit signals from their dendrites. No neuron ever has more than one axon; however in invertebrates such as insects the axon sometimes consists of several regions that function more or less independently of each other. Most axons branch, in some cases very profusely.

Axons make contact with other cells—usually other neurons but sometimes muscle or gland cells—at junctions called synapses. At a synapse, the membrane of the axon closely adjoins the membrane of the target cell, and special molecular structures serve to transmit electrical or electrochemical signals across the gap. Some synaptic junctions appear partway along an axon as it extends—these are called en passant ("in passing") synapses. Other synapses appear as terminals at the ends of axonal branches. A single axon, with all its branches taken together, can innervate multiple parts of the brain and generate thousands of synaptic terminals.

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