Mental Sweating

This topic came across my mind as I was studying for an Organic Chemistry test.

I thought, "Why do I get so tired after I study for a long time or if I take a long test?"

After all, I'm not working out, running, or playing hockey.  How can I be more tired after I take the SAT than after I play a hockey game?

After examining the question for a while, I tried to come up with a logical reason why brain function can tire me out.

At first I thought:

Well, I get tired after I use my muscles.  My brain must just be a muscle that expends energy.  Like my gastrocnemius or tounge.  But when I typed "Is my brain a muscle?" into Google, this is what I got:

"No.  Its composed of two things called gray matter and white matter, gray matter is made from the cell bodies of the nerve cells, and the white matter made from the bundles of their axons (which transmits the nervous signals to other neurons or effector cells"(site: WikiAnswers)

So, why/how does the brain need/get it's energy?

After a little more research, I learned a little bit more about it.

Your brain cells need two times more energy than the other cells in your body.

Neurons, the cells that communicate with each other, have a high demand for energy because they're always in a state of metabolic activity. Even during sleep, neurons are still at work repairing and rebuilding their worn out structural components.

They are manufacturing enzymes and neurotransmitters that must be transported out to the very ends of their– nerve branches, some that can be several inches, or feet, away.

Most demanding of a neuron's energy, however, are the bioelectric signals responsible for communication throughout the nervous system. This nerve transmission consumes one-half of all the brain's energy (nearly 10% of the whole body's energy).

Thank you Wikipedia!

Ok so now this makes a lot of sense!  The brain cells need two times the amount of energy that your normal cells need.  So, for every hour I spend totally devoted to studying or completely invested in a text, it is (time to break out the calculator!) like two hours of physical work.

Well, that is not entirely true because there is plenty of overlap in the types of work.  You use your brain to communicate with your muscles so you are using brain cells when moving.  Then you can't really know if it is just your brain making you tired during or after a test.

I know that I move my wrist, fingers and arm during a test to write my answers down.  
But surely that can't take up too much energy.  Can't it?

Maybe I unintentionally twitch my leg up and down while thinking about a question.
Again, how can only that be the cause of my exhaustion?

I was not doing any physically demanding processes at all during the test to have gotten that tired afterwards.  It must have been the thinking!

I want to call to your attention exactly how tired I got after taking the SAT.
Once I got home, I laid on the couch the rest of the afternoon watching movies and dozing off multiple times.  I didn't talk.  I didn't move.  I didn't even get up to get food when I was hungry.  All I wanted to do was nothing.

Now perhaps I was being a bit dramatic. (It is very likely given my dramatic nature) But I was very tired and I know I wasn't the only one who felt that way.

This was where I was going to give you an example of a person who just recently took the SAT and said she was tired and all she wanted to do was nap after the test and not move from her bed...

Well, when I called my sister to ask her about how she felt after taking the test, she said she was relieved.  That wasn't the answer I was going for so I asked her if she felt tired at all after taking the test...

She said no...

Well, now I don't know if I'm the crazy one or she is.

I'm leaning towards me being the crazy one.  And if that is true then why are you reading a crazy person's blog?

Not just any crazy person either.  Someone who thinks thinking is so physically demanding that he must sleep after taking tests.  I mean just thinking about this brain stuff has gotten me all tuckered out.

Happy Valentines day everyone!  
I love you all!