Final answer:
Psychoactive substances are drugs that affect the central nervous system by influencing neurotransmitters in the brain. They can cause alterations in mood, thinking, perception, and behavior. These substances include both legal and illegal drugs and are divided into different classes based on their effects.
Step-by-step explanation:
Pscyhoactive substances are a type of drug that affect the central nervous system by influencing neurotransmitters in the brain. These substances can alter mood, thinking, perception, and behavior. They include both legal substances like nicotine and alcohol, as well as illegal drugs like LSD and heroin. Psychoactive drugs can be divided into different classes based on their effects, including stimulants, depressants, hallucinogens, and more.