Final answer:
Alcohol is a central nervous system depressant with effects that range from sedation to potentially fatal respiratory depression. Caffeine and nicotine are stimulants that increase alertness and arousal. Marijuana has a mix of depressant and stimulant effects due to its components THC and CBD.
Step-by-step explanation:
Alcohol is a psychoactive substance classified as a depressant, which is known to slow down the central nervous system, impairing normal reflexes and alertness. It is commonly found in beverages like beer, wine, and spirits, and its active ingredient is ethanol. At lower doses, it may cause mild sedation and poor coordination, while higher consumption can lead to severe impairments and potentially fatal outcomes such as respiratory depression, coma, or death.
Caffeine is a central nervous system stimulant found in coffee, tea, and various energy drinks and medications. Unlike depressants, caffeine enhances alertness and wakefulness, making you feel more awake.
Nicotine is another stimulant, typically consumed through tobacco products like cigarettes. It affects the neurotransmitter acetylcholine, which contributes to increased alertness and arousal. However, repeated use can lead to addiction and various health issues.
Marijuana, which contains compounds like tetrahydrocannabinol (THC) and cannabidiol (CBD), can exhibit both depressant and stimulant effects. THC is the main psychoactive component that may cause euphoria and altered perceptions, while CBD has more calming effects and is used to treat conditions such as anxiety and muscle spasms.