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13.21: Drugs and the Nervous System

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Is coffee a drug?

Maybe. But that doesn't necessarily mean it is bad for you. Looks tasty, though. Other than taste, why do many people have a cup of coffee in the morning? Does it help them wake up? For many people, it does. Why? The caffeine in the coffee stimulates the central nervous system. This drug is one of the milder drugs affecting the nervous system.

Drugs and the Nervous System

A drug is any chemical that affects the body’s structure or function. Many drugs, including both legal and illegal drugs, are psychoactive drugs . This means that they affect the central nervous system, generally by influencing the transmission of nerve impulses. For example, some psychoactive drugs mimic neurotransmitters. At the link below, you can watch an animation showing how psychoactive drugs affect the brain. http://www.thirteen.org/closetohome/animation/neuron-main.html

Examples of Psychoactive Drugs

Caffeine is an example of a psychoactive drug. It is found in coffee and many other products (see Table below ). Caffeine is a central nervous system stimulant . Like other stimulant drugs, it makes you feel more awake and alert. Other psychoactive drugs include alcohol, nicotine, and marijuana. Each has a different effect on the central nervous system. Alcohol, for example, is a depressant . It has the opposite effects of a stimulant like caffeine.

Product Caffeine Content (mg)
Coffee (8 oz) 130
Tea (8 oz) 55
Cola (8 oz) 25
Coffee ice cream (8 oz) 60
Hot cocoa (8 oz) 10
Dark chocolate candy (1.5 oz) 30

Drug Abuse and Addiction

Psychoactive drugs may bring about changes in mood that users find desirable, so the drugs may be abused. Drug abuse is use of a drug without the advice of a medical professional and for reasons not originally intended. Continued use of a psychoactive drug may lead to drug addiction , in which the drug user is unable to stop using the drug. Over time, a drug user may need more of the drug to get the desired effect. This can lead to drug overdose and death.


  • Drugs are chemicals that affect the body’s structure or function.
  • Psychoactive drugs, such as caffeine and alcohol, affect the central nervous system by influencing the transmission of nerve impulses in the brain.
  • Psychoactive drugs may be abused and lead to drug addiction.


Use this resource to answer the questions that follow.

  1. Describe the effects of each of the following on the nervous system:
    1. alcohol
    2. cocaine
    3. opiates
    4. marijuana


1. What is a psychoactive drug? Give two examples.

2. Define drug abuse. When does drug addiction occur?

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At Grade


Date Created:

Feb 24, 2012

Last Modified:

Jul 30, 2014
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