When stimulants are taken, they increase the amount of chemicals, called neurotransmitters, that control how the brain functions. These chemicals cause the brain to become more active and result in increases in alertness, attention and energy.

Don't forget to check out Allie's report on the brain.

This is why taking high doses of a stimulant can have dangerous physical effects, such as extremely high body temperatures, irregular heartbeat, heart failure, seizures, or death!

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