For years we have been fascinated with the brain and how it works. It is only recently (the past couple of decades) that the technology exists to allow us to look at the brain of a living person and begin to understand what’s happening. Suffice it to say, there’s way more we don’t know than we know, but the research is ongoing and information is increasing exponentially.
We’re going to look at the structure and function of the brain as a way of moving into a discussion of mental illness. Please don’t take anything I say to a doctor, nurse, psychiatrist or medical professional, because they’ll laugh. <vbg> I’m going to leave out a whole bunch and put the rest in layman’s terms so that we can use this information as writers.
So let’s begin
There are a number of types of cells in the brain, all with very specialized functions. Brain cells, aka neurons, is one of these; their sole purpose is to transmit the electrical impulses of the brain. This electrical activity controls everything we do, think and feel.
There are about 100 billion of these specialized cells and each interacts with about another thousand cells! They interact with each other in neural or neuronal pathways (depending on the expert’s word choice). In the real world, you’ve seen the equivalent of these pathways: cows always walk the same path to return to the barn. In the city, people always walk the same path when they’re cutting the corner of a lot or a park. On those pathways the grass is dead and a rut is worn into the earth.
No soil in your brain, but the same kind of thing happens. Cells communicate with each other. The more two specific cells communicate (ie share electricity) the stronger the path. Over time, those paths become the only way these two neurons communicate. As a result, we see what we expect, fill in the missing pieces etc. This is also why it’s so hard to stop the negative self talk – it follows a neural pathway over and over and over again. You know how long it takes the grass to grow back into a worn path. It takes longer than that to dismantle a neural pathway. By the way, the simplest example of a simple neural pathway is the knee jerk reaction when the doctor taps your knee.
There are three parts to these brain cells: The dendrites, body and axon.
The cell body is the main part of the brain and functions as any other cell body. This is the ‘gray matter’ we so often hear about in reference to the brain.
Dendrites take in the electrical charge and axons pass it on to the next cell. But it is rarely a 1:1 exchange. Each neuron can take input from multiple cells and pass it on to multiple cells. As with any interaction, if the same information comes into the cell from multiple sources, the information (or charge) is increased and amplified. But if the sources provide conflicting information, the strength of the charge may be diminished or neutralized. This is the same as having colored water. If you add more color to the water, the color deepens. But if you add more water, the color is lightened. (On the diagram above, the dendrites are on the top half of the picture, above the cell body.)
Axons are long, thin, cable-like projections from the cell body which carry the electrochemical messages along the length of the cell. Depending upon the type of neuron, axons can be covered with a thin layer of myelin which is a type of fat that insulates the axon. Myelin helps to speed transmission the charge down the axon. Myelinated neurons are typically found in the peripheral nerves (sensory and motor neurons), while nonmyelinated neurons are found within the brain and spinal cord. (This is the long tail below the cell body.)
One other little detail: If any of the sheath falls off, the result is Muscular Sclerosis. When you think of all the myelin in the brain (and that’s why we all need some fat in our food) it is easy to see why it’s so hard to diagnose MS and why the symptoms can be varied and progressive.
The axons can extend from your finger tip to the brain. Or they can be micro-millimeters long.
The axon and dendrites never touch. The small space between them is called the synaptic cleft. Since these cells sit in cerebrospinal fluid (don’t you just love that word?) which is proteins and sugar in a liquid, an electrical charge isn’t safely transmitted between neurons. To ensure this communication, the sending neuron surrounds the charge with a neurotransmitter, of which there are more than 100 in the brain. The accepting neuron takes in the charge but doesn’t want the neurotransmitter, which is left in the brain fluid.
Given that the amount and consistency of the brain fluid is critical to healthy functioning, the axon terminal which released the neurotransmitter takes it back in. This process is called reuptake.
The neurons take in information from the environment, usually through our five senses and pass it along to the appropriate parts of the brain to make decisions. For example: last week the cells in my thumb realized the boiling water I had touched was hot. It sends that message to the neurons in the brain, which told me to pull my thumb out of the hot water. And this all happened in a nano-second.
Isn’t it amazing?
Again, I’ve kept this simple and hopefully light so you’re not all running to the hills screaming about the biology of the brain. I hope you found it the least bit interesting. And it will be useful as we move forward in our discussion.
By the way, I used the following sites to confirm what I knew and correct what I had wrong:
photo credit: <a href=”http://www.flickr.com/photos/juliendn/3347475063/”>juliendn</a> via <a href=”http://photopin.com”>photo pin</a> <a href=”http://creativecommons.org/licenses/by-nc-sa/2.0/”>cc</a>