The Brain, Part Two

Happy Brain Awareness Week, everyone! No joke, March 15th- 21th is really, truly brain awareness week- and I didn't make this up.

I have just discovered that there is a book from the Society for Neuroscience that you can read online! It is called Brain Facts and is supposed to be a (74 page long) introduction to neuroscience. Pretty amazing, isn't it?

Oh, my brain hurts- figuratively. The lesson for part two shall be neurons. Neurons are the cells that make up your brain- cells, if you recall, are not just stuff, but the basic units of life. Before you jump on me with a dozen "neurons aren't the only stuff in your brain," though, note that, yes, neurons aren't the only stuff in your brain. However, they are the most well known and are the basic working cell in your brain. There are three main parts: the cell body, or soma, the axon, and dendrite. The cell body is something we should be familiar with, since we covered cells in genetics: it contains the nucleus and the organelles. Dendrites and axons are specialized extensions (like an arm and a leg, but neurons don't walk) of the neuron. Wait, a picture would help, wouldn't it? Here we go:

Dendrites, those little things that branch out from the cell body, receive signals from other cells. The axon sends signals out. Think of it this way: dendrites in, axons out. Simple enough, right? Take a breather to put that in your head. Ready? The points at which two cells contact each other is called a synapse. I say contact because they don't actually touch. Now, this vocabulary is nice and all, but how do the cells work, you ask? Good question- I don't really know. The gist of what I do know, however, is that the nerve cell, when at rest, has a natural (I believe negative, though I'm not so sure) charge. However, when a cell sends a signal to the neuron, it generates an electric charge that goes to end of the axon, what the diagram depicts as the presynaptic terminal, which then releases neurotransmitters (chemicals) to the next neuron, which generates an electric charge, etc. If you want something more detailed, check out this website about the action potential, which explains how electrical pulses move along a neuron. In fact, if someone can explain how action potential works to me, I'd be delighted! In order to help the electric charge move along, the axon is covered in a sheath of mylelin. As the neurotransmitters (remember, chemicals) are released at the presynaptic terminal in little packets called quanta, it travels across a little gap called the synaptic cleft and binds to receptors on the next cell, which may cause that cell to fire an electric charge as well. Now, I don't know about you, but it's going to take a little while for that to soak in my brain. Look for more information in Part Three of The Brain!

Disclaimer: Seeing as I'm a student, this information may be invalid or not quite true- I'm still trying to figure it out and organize my thoughts in these posts!
Sources: http://www.sfn.org/skins/main/pdf/brainfacts/2008/brain_facts.pdf

http://nobelprize.org/educational_games/medicine/nerve_signaling/

http://faculty.washington.edu/chudler/cells.html