Monday, 8 October 2012


Caffeine is everywhere. Coffee. Tea. Soda. Chocolate. Those crazy energy drinks that undergraduate computer science students chug like water. I don't know many kids who like coffee, but I know lots of kids who like soda and chocolate.

Check out what happens to spiders when they're on caffeine:

The web on the left was made by a spider who'd never had caffeine. The web on the right was made by a caffeinated spider.

But what is caffeine? It's a chemical in chocolate and soda, yes. But what does it do to your brain? Because as soon as you feel that jolt, something's happening in your brain. Caffeine is what neuroscientists call a "stimulant". This means that it wakes you up. How?

Your brain needs energy to work. It gets this energy from a chemical called adenosine triphosphate, or ATP. Your neurons make ATP from the food you eat. When your neurons need energy, they break a molecule of ATP. This is kind of like snapping a twig. When you snap a twig, you hear a noise and feel a jolt. The noise and jolt are both types energy that are released by snapping the twig. When your neurons break ATP, there is energy released. But instead of being wasted in a snapping sound, your neurons harness that energy and use it to do all the work that neurons do.

Adenosine triphosphate (ATP). ATP is made from adenosine (which is adenine and ribose - the blue and pink) and three phosphate groups (the yellow circles). Breaking off the phosphate groups produces energy, which the neurons need to work. Adenosine is left over.
What's left over from the breaking of ATP is a molecule called adenosine. As you use more and more energy, the adenosine in your brain builds up. Your brain senses this big increase in adenosine. It knows that if adenosine levels are high, it means you've been working hard for a long time. Which means it's time to sleep! So it makes you feel tired, and the next thing you know, you're in dreamland.

This is where caffeine comes in. It stops neurons from sensing adenosine. If neurons can't sense adenosine, they don't know you're supposed to be tired. So you stay awake, typing blog posts until late in the night even though you have work at 8 am. Oh, wait....that's just me. But the point is, caffeine wakes you up by making your neurons insensitive to adenosine. It doesn't give you energy. It stops your brain from noticing that you're out of energy.

Caffeine has other effects, too. It increases the activity of certain neurotransmitters. Neurotransmitters are the chemicals that neurons use to talk to each other. Glutamate is a neurotransmitter important for learning and memory. Dopamine is a neurotransmitter that gives you feelings of pleasure and reward. Caffeine increases neurotransmission of both glutamate and dopamine. The result? First, you get really good at studying. Second, you feel happy. And both those things make you want more caffeine. Because of the dopamine effect in particular, caffeine is addictive.

Caffeine has some annoying side effects outside of the brain, like increasing heart rate and giving some people upset stomachs. Plus, if you're addicted to caffeine and stop drinking it, you become head-achy and cranky and no fun to be around. So it's a good idea to limit the amount of caffeine you eat or drink, especially if you're a kid. Kids are more sensitive to the effects of caffeine - including the bad effects - than adults. But if someone tells you that caffeine stunts your growth, you can go ahead and tell them that's a myth.

Caffeinated soda (pop, soft drink, whatever you call it) works by tricking your brain into thinking you have energy to burn.


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