Final answer:
Caffeine and nicotine are stimulants that enhance brain activity and alertness, unlike depressants and anxiolytics, which calm the brain and reduce anxiety, and euphoriants, which produce feelings of well-being.
Step-by-step explanation:
Depressants, anxiolytics, and euphoriants are NOT things like caffeine, nicotine, beer, and tranquilizers.
Caffeine and nicotine are stimulants that increase alertness, wakefulness, and have an excitatory effect on the neurons and cardiac centers. Specifically, caffeine increases the rates of depolarization at the SA node, and nicotine stimulates the sympathetic neurons that affect the heart. On the other hand, depressants like alcohol (found in beer) and opioids reduce brain activity, induce sleepiness, and can create a feeling of calm.
Anxiolytics are drugs used for their tranquilizing effects, such as benzodiazepines, which help to inhibit anxiety. While euphoriants such as MDMA and certain amphetamines trigger intense feelings of well-being.