1. Psychoactive Drugs
Because the nervous system interacts with every other system of the body, dysfunction of any of its parts can have numerous effects.
A drug is a chemical that alters body structures or biological functions. Psychoactive drugs alter the functioning of the CNS and have a significant effect on the mind or behavior.
Many psychoactive drugs produce physiological dependence and addiction when abused.

2. Psychoactive Drugs, continued
Depressants, such as alcohol and barbiturates, are psychoactive drugs which decrease the activity of the central nervous system. High doses of depressants can depress respiratory function enough to cause death.
Stimulants, such as cocaine and nicotine, generally increase the activity of the central nervous system. At high doses, stimulants can be fatal.
Inhalants, such as glue, are psychoactive drugs which cause disorientation, brain damage, and respiratory failure.

3. Psychoactive Drugs, continued
Cigarette smoke contains nicotine. Nicotine is a highly addictive and very toxic stimulant which mimics the action of an important neurotransmitter and causes permanent changes in the brain.
In addition to the neural changes attributed to nicotine, toxins in cigarette smoke cause mouth cancer, heart disease, lung cancer, and emphysema.

4. Psychoactive Drugs, continued
Alcohol is a depressant that impairs coordination, judgment, and speech.
Continued alcohol consumption eventually produces a state of intoxication known as being “drunk.”
Alcohol affects neurons throughout the brain and changes the way certain receptors work.

5. Effects of Blood Alcohol Concentration

6. Psychoactive Drugs, continued
The active ingredient in marijuana is commonly known as THC. THC is a psychoactive drug which causes disorientation, impaired judgment, short-term memory loss, and general loss of motivation.
Narcotics are a class of psychoactive drugs that are extremely addictive. Some of the most potent narcotics are derived from a type of poppy plant that produces a substance called opium.

7. Psychoactive Drugs, continued
Drugs derived from opium include codeine, morphine, and heroin.
Morphine is one of the most effective pain-relieving drugs used today. Narcotics like morphine block pain because they mimic the action of a class of neurotransmitters called enkephalins.
Enkephalins bind to neurons in the spinal cord and prevent pain signals from reaching the brain.

8. Psychoactive Drugs of Abuse

9. Neural Changes
Addiction is a physiological or psychological dependence on a substance. Addiction occurs when repeated use of a drug alters the normal functioning of neurons and synapses.
Tolerance to a drug occurs when increasing amounts of the drug are needed to achieve the desired effect.
Withdrawal is the set of emotional and physical symptoms that occur when a drug is removed from the body. Common symptoms include vomiting, headache, and depression.

10. Neural Changes, continued
Cocaine is a highly addictive stimulant because it affects the release of dopamine from neurons in the brain that play an important role in the sensation of pleasure.
Continued cocaine use decreases the number of dopamine receptors in the brain which results in the postsynaptic cell becoming understimulated.
Cocaine addiction occurs because more cocaine must be taken to maintain adequate stimulation of postsynaptic cells.

11. Neurons and Cocaine Addiction