Introducing the Nerve Cell

The brain is composed largely of nerve cells, or neurons. They look like this:

As you can see, neurons are kind of funny looking. They have a fat body with lots of branches coming off it (dendrites) and one really long leg that extends out from the cell body, the axon.

Dendrites receive connections from other nerve cells.

Axons connect nerve cells to other nerves or tissues.

These connections allow the nerves to transmit their signals all over the body. This is why you can wiggle your toe: The command comes from your brain and creates an electrical impulse that is transmitted by various neurons until the message gets to your toe to wiggle.

Similarly, when someone tickles your foot, a different set of nerve cells transmit the feeling from your foot back to your brain.

Remember those long axons in the nerve cells? They work by carrying electrical impulses to, from and across the brain. Your spinal cord is basically a giant bundle of axons.

The amazing thing is that the speed at which an axon can carry its electrical impulse depends on the development of a layer of fat around it. That fatty layer, called myelin, can accelerate the transmission of signals by up to 100 times.

Myelin develops over time, and grows thicker the more a neural pathway is used. This is one of the biggest differences between teen and adult brains: teenage brains are not fully myelinated.

In our next article we will look at myelin itself, how it develops and what it shows us about the teen brain.

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Photos:

“Nerve Cell Diagram” http://www.thomasjwestmusic.com/neurologyapplied.htm

“774 – Neuron Connection – Pattern” by Patrick Hoesly, under a CC BY 2.0 license. http://www.flickr.com/photos/zooboing/4743616313/

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