What effect does caffeine have on the central nervous system?

Caffeine acts as a stimulant to the central nervous system, which means it increases alertness, energy, and cognitive function. It achieves this primarily by blocking the action of adenosine, a neurotransmitter that promotes sleep and relaxation. When adenosine is inhibited, the levels of other neurotransmitters such as dopamine and norepinephrine increase, leading to heightened alertness and improved mood.

This stimulating effect is why caffeine is commonly consumed in beverages like coffee and tea, especially when people seek to overcome fatigue and enhance concentration. In contrast, caffeine does not induce sleepiness, act as a depressant, or enhance memory while decreasing alertness, which aligns with its well-documented role as a cognitive enhancer.