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Introducing... Your Brain

The brain is the command center of your body. It weighs about three pounds, and has different centers or systems that process different kinds of information.

The brain stem is the most primitive structure at the base of your brain. The brain stem controls your heart rate, breathing, and sleeping; it does the things you never think about.

Various parts or lobes of the brain process information from your sense organs: the occipital lobe receives information from your eyes, for example. And the cerebral cortex, on top of the whole brain, is the "thinking" part of you. That's where you store and process language, math, and strategies: It's the thinking center. Buried deep within the cerebral cortex is the limbic system, which is responsible for survival: It remembers and creates an appetite for the things that keep you alive, such as good food and the company of other human beings. [1], [2]

The cerebellum is responsible for things you learn once and never have to think about, such as balance when walking or how to throw a ball.

How Does Your Brain Communicate?

The brain's job is to process information. Brain cells called neurons receive and send messages to and from other neurons. There are billions of neurons in the human brain, each with as many as a thousand threadlike branches that reach out to other neurons.

In a neuron, a message is an electrical impulse. The electrical message travels along the sending branch, or axon, of the neuron. When the message reaches the end of the axon, it causes the release of a chemical called a neurotransmitter. The chemical travels across a tiny gap, or synapse, to other neurons.

Specialized molecules called receptors on the receiving neuron pick up the chemical. The branches on the receiving end of a neuron are called dendrites. Receptors there have special shapes so they can only collect one kind of neurotransmitter.

In the dendrite, the neurotransmitter starts an electrical impulse. Its work done, the chemical is released back into the synapse. The neurotransmitter then is broken down or is reabsorbed into the sending neuron. [1], [2]

Neurons in your brain release many different neurotransmitters as you go about your day thinking, feeling, reacting, breathing, and digesting. When you learn new information or a new skill, your brain builds more axons and dendrites first, as a tree grows roots and branches. With more branches, neurons can communicate and send their messages more efficiently. [1]

What Do Drugs Do to the Brain?

Some drugs work in the brain because they have a similar size and shape as natural neurotransmitters. In the brain in the right amount or dose, these drugs lock into receptors and start an unnatural chain reaction of electrical charges, causing neurons to release large amounts of their own neurotransmitter.

Some drugs lock onto the neuron and act like a pump, so the neuron releases more neurotransmitter. Other drugs block reabsorption or reuptake and cause unnatural floods of neurotransmitter. [1]

All drugs of abuse, such as nicotine, cocaine, and marijuana, primarily affect the brain's limbic system. Scientists call this the "reward" system. Normally, the limbic system responds to pleasurable experiences by releasing the neurotransmitter dopamine, which creates feelings of pleasure.

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