How does a neuron work?
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Wings for Life will regularly publish “illustration guides” designed to help non-scientists understanding how the spinal cord works, how the injury alters it and finally which different approaches scientists are taking to find a cure for spinal cord injury. The first illustration guide will explore the basic structure and functioning of a neuron.
A neuron (also known as nerve cell) is an electrically excitable cell that takes up, processes and transmits information through electrical and chemical signals. It is one of the basic elements of the nervous system.
In order that a human being can react to his environment, neurons transport stimuli. The stimulation, for example the burning of the finger at a candle flame, is transported by the ascending neurons to the central nervous system and in return, the descending neurons stimulate the arm in order to remove the finger from the candle.
A simple structure designed for a complex task
A typical neuron is divided into three parts: the cell body, the dendrites and the axon. The cell body (green color), the center of the neuron, extends its processes called the axon and the dendrites to other cells. Dendrites typically branch profusely, getting thinner with each branching (blue color). The axon is thin but can reach enormous distances (violet color).
To make a comparable scale, the diameter of a neuron is about the tenth size of the diameter of a human hair.
Getting really into it
The cell body is the central part of the neuron. It contains the nucleus of the cell (that carries all the genetic material) and numerous organelles that allow protein synthesis (endoplasmic reticulum, golgi, etc) and energy production (mitochondria).
The axon is a fine, cable-like projection that can extend over enormous distances. At its final tip, the axon contacts other cells (nerve- or muscle cells), through structures named synapses.
The cell body and the axon are supported by a complex network of structural proteins called microtubules.
All neurons are electrically excitable. The electrical impulse mostly arrives on the dendrites, gets processed into the cell body to then move along the axon.On its all length an axon functions merely as an electric cable, simply transmitting the signal. Once the electrical reaches the end of the axon, at the synapses, things get a little more complex.
The key to neural function is the synaptic signaling process, which is partly electrical and partly chemical. Once the electrical signal reaches the synapse, a special molecule called neurotransmitter is released by the neuron. This neurotransmitter will then stimulate the second neuron, triggering a new wave of electrical impulse, repeating the mechanism described above.
… next month
The next “Illustration Guide” will focus on an essential partner of a neuron: the oligodendrocyte.
Text: Vieri Failli, Verena May, Rosi Lederer
Graphics: Vieri Failli