Final answer:
Stimulants increase brain activity and alertness, while depressants calm the brain and induce sleepiness.
Step-by-step explanation:
Stimulants are drugs that stimulate the brain and increase alertness and wakefulness. Examples of stimulants include caffeine, nicotine, cocaine, and amphetamines such as Adderall.
Depressants are drugs that calm the brain, reduce anxious feelings, and induce sleepiness. Examples of depressants include ethanol (in alcoholic beverages) and opioids such as codeine and heroin.
The effects of stimulants and depressants differ in terms of their ability to increase or decrease neural activity and their impact on brain and body functions.