Meet your incredible brain: check out command central for everything you do. (Heads Up Real News About Drugs and Your Body).

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.

RELATED ARTICLE: YOUR BRAIN: PIECE BY PIECE

IN CHARGE: 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.

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.

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.

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.

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.

IT'S A HABIT:

The cerebellum helps with everyday tasks you do over and over. Once you've learned how, you don't realty 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.

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.

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).

The Pleasure Center

If you've ever sunk a basket, held bands 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.

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 Brian

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.

In addition to damaging the way you process pleasure, drugs can damage your brain and body in many other ways. So don't be fooled. And keep reading to learn more.

AMAZING FACTS

* When you're born, your brain weighs about a pound. But by age six, it weighs three pounds. What happens? Learning to stand, talk, and walk creates a web of connections in your head--two pounds worth!

* Your brain weight accounts for about two percent of your body weight. But your brain uses 20 percent of your body's oxygen supply and 20 to 30 percent of your body's energy.

* Your brain has about 100 billion neurons. A typical brain cell has from 1,000 to 10,000 connections to other brain cells.

* The right side of your brain controls the left side of your body, and the left side of your brain controls the right side of your body.

* Your brain is full of nerve cells, but it has no pain receptors. Doctors can operate on your brain while you're awake-and you won't feel a thing!

* A message for action travels from your brain to your muscles as fast as 250 miles per hour.

* If you ironed out all the wrinkles in your brain, it would have an area of about two and a half square feet. It feels like soft butter.