National Certified Addiction Counselor, Level I (NCAC I) Practice Exam 2025 – Comprehensive All-in-One Guide to Exam Success!

Caffeine primarily acts as a central nervous system stimulant, and one major mechanism of action is its ability to increase norepinephrine levels. By blocking adenosine receptors in the brain, caffeine reduces feelings of drowsiness and fatigue, which enhances alertness and wakefulness. This antagonism of adenosine leads to an increase in the release of other neurotransmitters, including norepinephrine, which plays a crucial role in mood regulation and the body’s fight-or-flight response. The elevated levels of norepinephrine can also contribute to increased heart rate and energy, further demonstrating how caffeine can stimulate the central nervous system and enhance cognitive function.

Other options are less relevant to caffeine's primary action; for instance, caffeine does not significantly increase blood vessel dilation—rather, it can cause temporary constriction in some areas. It also does not work by blocking serotonin effects; instead, it influences alertness primarily through its effect on adenosine. Lastly, caffeine does not decrease dopamine production; on the contrary, it often results in increased dopamine activity, leading to improved mood and alertness.