Why does caffeine keep us awake?

Caffeine, a central nervous system stimulant, keeps us awake by blocking the effects of adenosine, a neurotransmitter that promotes sleep. Adenosine levels rise throughout the day, making us feel tired and ready for sleep at night. Caffeine binds to adenosine receptors in the brain, preventing adenosine from binding and causing sleepiness. This blocking effect increases neural activity and alertness, making it harder to fall asleep or stay asleep. Caffeine can also interfere with the body's circadian rhythm, disrupting the natural sleep-wake cycle. Consuming caffeine in the hours leading up to bedtime can significantly impact sleep quality and quantity, making it harder to get a restful night's sleep.