Meet your incredible brain: check out command central for everything you do

Science World, Oct 18, 2002 by Kathy Kukula

What's that gray, wrinkled blob inside your skull? It's your brain the body's most amazing organ, a three pound factory for feelings, memories, ideas, and movement. It makes your heart beat, stores the beat to your favorite song, and prompts you to "beat it" when you sense danger. Your muscles may seem smart when you hit a home run or learn a dance step, but every instruction comes from your brain.

Your brain is always changing--and growing. New experiences create new connections between brain cells, adding to a dense web of brain tissue. There's no end to what you can learn: One brain cell, or neuron, can have thousands of connections, or synapses, with other brain cells. Messages zip from neuron to neuron, carrying information to and from your muscles and sense organs, and from brain part to brain part.

In short, the brain is an intricate machine. Check out what goes on inside your head.

YOUR BRAIN: PIECE BY PIECE

IN CHANGE: The cerebral cortex is the largest part of your brain. It sits like a mushroom cap on the rest of your brain and takes up about two thirds of the total mass. This is where you think and reason. It's where you create the kind of movements you have to think about, like playing the piano or flipping your skateboard. Parts of the cerebral cortex also control seeing, hearing, and touching.

THE FEELINGS BRIDGE: The limbic system is like a bridge between your thinking brain--the cerebral cortex--and the parts of your brain that control your body's physical systems. This makes it easy for strong feelings--such as pleasure, fear, or attraction to other people--to cause reactions in your stomach, muscles, and heart.

Remember: The hippocampus, which is part of the limbic system, receives and stores long-term memories. So, if you remember your teachers' names from last year, you're using the hippocampus.

Plan and Reason: The prefrontal cortex helps you plan ahead. This is where you consider the consequences of your actions. This part of your brain doesn't finish developing until you're 20.

THE BASICS: Your brain stem is the lowest part of your brain, just above your spinal cord. This structure takes care of basic functions such as the heartbeat, breathing, and digestion.

Move: When you think about moving your body, the motor cortex tells your muscles what to do. Precise moves, like typing, or playing an instrument, use lots of brain cells.

Sense: The posterior parietal cortex is a processing center that makes sense of what you're feeling, smelling, and hearing, and connects those sensations to memories and ideas.

IT'S A HABIT: The cerebellum helps with everyday tasks you do over and over. Once you've learned how, you don't really have to think about how to ride a bike, dribble a basketball, or comb your hair. There's constant messaging, between the cerebellum and parts of the cerebral cortex, so you can adjust your actions when conditions change.

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Instant Messages--IMs in Your Brain

How do brain cells get their messages across? Messages travel through brain cells, also called nerve cells or neurons, as electricity. Neurons have threadlike fibers called axons that send messages and branches called dendrites that receive them. To make messages jump from cell to cell--when your brain signals your hand to scratch your head, for example--your brain creates chemicals called neurotransmitters. Whenever you think or act, axons release these chemicals. Dendrites have receptors, like custom-made garages, into which each chemical fits. A fatty white coating called myelin covers many axons; it helps messages move quickly, especially along the long axons that connect to muscles.

The Pleasure Center

If you've ever sunk a basket, held hands with someone special, or bitten into a juicy cheeseburger, you may remember the rush of pleasurable feelings those events created. These good feelings are a key to your survival--after all, if you eat well, you'll live longer, and most of us think of eating as a pleasurable experience.

Unlike remembering, say, your history homework, you remember pleasure more quickly because of a chemical called dopamine. Dopamine works in the pleasure center in the middle of your brain (see the limbic system on the diagram at left).

Once you've had a "feel-good" experience, your brain builds a new path, like a shortcut. That's why you'll start to feel good the next time you just pick up a basketball, smell the cheeseburger, or see your crush in the hall. Your senses send signals, and the dopamine starts flowing. You've wired your brain to repeat what brings good feelings. You smile just thinking about it!

Drugs Fool Your Brain

Different drugs act on the brain in different ways. But all drugs of abuse have one thing in common: they act on the way the brain experiences pleasure. Drugs make people "high" by invading and manipulating the brain's pleasure circuitry. They fool your brain into good feelings that are a reaction to chemicals, instead of to real experiences.

The key word is "fool." Drug abuse can damage the brain's wiring for pleasure, making it unable to function in a healthy, normal way. You can become addicted, meaning that your craving for the feeling you get from a drug will become so strong that you'll risk serious consequences to get it. And your ability to feel pleasure the old-fashioned way--the real way--may be disrupted. Good food, real accomplishments--even true love--may leave you feeling flat.