"A heroin overdose happens because use of the drug alters the neurons within every addict's brain—but the alterations occur in different parts of the brain at varying rates of speed."

So explains Susan Brink in National Geographic, in debunking some of the common misconceptions about the kind of overdose that likely killed the actor Philip Seymour Hoffman. An accidental overdose, in fact, is not as simple as an addict simply consuming too much. 

"The pleasure center, increasingly hard to satisfy, is screaming "More!" Brink explains. "But primitive centers that control breathing and heart rate are not building up tolerance at the same pace and are whispering "Enough."

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In the video below, professor Carl Hart talks about the right way and the wrong way to define a drug addiction.

Watch the video here:

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