Neuron

Neurons (also spelled neurones or called nerve cells) are the primary cells of the nervous system.

Anatomy and histology

Many highly specialized types of neurons exist, and these differ widely in appearance.

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Characteristically, neurons are highly asymmetric in shape. Neurons consist of:

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• The dendrite, a short, branching arbor of cellular extensions. Each neuron has very many dendrites with profuse dendritic branches. These structures form the main information receiving network for the neuron.
• The soma, or cell-body, the relatively large central part of the cell between the dendrites and the axon.
• The axon, a much finer, cable-like projection which may extend tens, hundreds, or even tens of thousands of times the diameter of the soma in length. This is the structure which carries nerve signals away from the neuron. Each neuron has only one axon, but this axon may undergo extensive branching and thereby enable communication with many target cells.

Axons and dendrites in the central nervous system are typically only about a micrometre thick, while some of those in the peripheral nervous system are much thicker. The soma is usually about 25 micrometres in diameter and not much larger than than the cell nucleus it contains. The axon of a human motoneuron can be over a metre long, reaching from the base of the spine to the toes, while giraffes have single axons running along the whole length of their necks, which is several feet.

Related Topics:
Micrometre - Cell nucleus - Motoneuron - Giraffe

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