Sci has been intending to do one of these posts for a while. I seem to spend ages talking about neurons, synapses, action potentials, connections, neurotransmitters, and different brain areas. But for all that, a lot of people don't really know what a neuron looks like and where the connections are taking place. So it's time to get back to basics. And that means a neuron (of course, things can get WAY more basic and in turn get more complicated, but we're sticking with the neurons for now).
And to help me out with this, I'm gonna take my first hack at Vuvox, a program allowing me to make an interactive collage. I saw Ed try it out to great effect for a post on ants as rafts (yes, AS rafts, it's awesome, go look), and I knew I HAD to try this one myself.
Here's what I've got:
The full text of the entry, with pictures in order and minus the popouts, is below. But it's much cooler up there, huh?
Welcome to...THE NEURON
The tissue of your brain is composed of neurons (what we're looking at today), and glial cells (which I will have to cover some other time). Neurons are specialized cells which are electrically excitable, and can use that electric excitability to received and transmit information. We are used to thinking of neurons as being the most important information transmitting cells in the brain...but it looks like glia may play a much bigger role than we think. But until science is clearer on glia, it is ONWARD to the neuron.
While many images of neurons and their connections might seem disorganized (though very pretty!), in fact the connections in your brain are highly organized and very tightly controlled during development and adulthood. Even the structure of individual neurons varies, from small and relatively simple, to elaborate tree-like structures which string across large distances and many different cell layers.
At its most basic, a neuron is a basic cell body, which is surrounded by different types of processes which emerge from it.
The main cell body here is called the soma. This is the part of the neuron that is most like other cells found in your body, containing a nucleus with chromatin and DNA, mitochrondia, and apparatus for translating DNA to RNA to protein, and transporting those proteins and other chemicals formed in the soma to other areas of the cell.
Emanating from the soma are the dendrites. These are thin, filamentous structures that branch a lot, getting thinner and thinner as they do so. The overall shape and structure of the dendrites forms what is called a "dendritic tree". Dendrites are thought to be mostly receivers of information from neuronal connections, translating a chemical signal into an electrical one, and transmitting the electrical signal down to the soma, or beyond to the axon.
Beyond the soma lies the axon, a single, long process heading off to a remote location (dendrites are, on the other hand, very local). The electrical signals known as action potentials are propagated along the axon, assisted by myelin, glial cells which wrap around the axon and leave spaces called "Nodes of Ranvier" allowing the electrical signal to "jump" from node to node along the process, greatly increasing the speed at which the signal can be sent.
At the end of the axon we come to the axon terminal, where the synapse is located. The axon terminal can be very widespread and any given neuron can make thousands of connections here. Each connection is called a synapse.
At the synapse, the electrical signal that went down the axon becomes a chemical one, as chemicals are released from the end of the axon terminal on one side of the synapse to contact the dendrites of other neurons on the other side.
Once contact is made and the other neurons are stimulated, the process starts over, with electrical signals running from the dendrites to the cell body, and from there down the axon and to other neurons.
So there you have it! Neurons are wonderful, electrical things, processing everything that happens in our environment, and allowing us to experience everything around us.