Everyone already has an idea of the meaning of the word drug. In common parlance, of all days ( "Oh what the hell" or "right now drug" or "this drug is not worth anything!") Drug has a meaning of something bad, not quality. Already in medical language, drug is almost synonymous with medicine.

The term originated in drug droog word (former Dutch) which means a dry leaf, because this formerly almost all medicines were made based on vegetables. Currently, drug medicine defines as: any substance that is capable of modifying the function of living organisms, resulting in physiological changes and behavior. The word psychotropic is composed of two others: and psycho tropic. Psycho is easy to understand because it is a Greek word that means our psyche (what we feel, do and think, ultimately what each one is). But the tropics is not as some may think, on the tropics, tropical climate... The word tropics here relates to the term tropism it means to pull through.

So psychotropic means attracting the psyche and psychotropic drugs are those that act on our brains by changing our way of feeling, thinking and, often, to act. But these changes in our psyche is not always in the same sense and direction. Obviously they depend on the type of psychotropic drug that was ingested. The Central Nervous System (CNS), contained in the skull, the main organ the brain. Depending on the action in the brain, psychotropic drugs are divided into three major groups.

The first group is that of drugs that decrease the activity of the brain, or depress the functioning, which means that the person who uses this type of drug is "off", "slow", uninterested in things .

So these drugs are called that depress activity of the central nervous system.

A second group of psychotropic drugs are those that act by increasing the activity of the brain, or stimulate the functioning causing a person who uses these drugs be "linked", "power" without sleep. So these drugs are named Stimulating the Activity of Central Nervous System.

Finally, a third group, consisting of those drugs that act by modifying qualitatively the activity of our brain, it is not therefore as quantitative changes to increase or decrease brain activity. Here is the change in quality. The brain starts to work outside their normal and brain activity is disturbed. Therefore this third group of drugs is called Disruption of activity of Central Nervous System.