What makes caffeine prevent sleep?

Caffeine functions by altering brain chemistry. It inhibits a natural brain chemical linked to sleep. This is the mechanism behind its effects.

In the Mytour article How Sleep Works, you discovered that adenosine attaches to brain receptors. This attachment induces drowsiness by reducing nerve cell activity. Additionally, adenosine binding causes brain blood vessels to expand, likely to increase oxygen flow during sleep.

Daily activities generate adenosine. For instance, the article How Exercise Works explains how muscles create adenosine as a byproduct of physical exertion.

Caffeine mimics adenosine to nerve cells, binding to their receptors. Unlike adenosine, it doesn't reduce cell activity. With caffeine occupying these receptors, cells can no longer detect adenosine, leading to increased activity. Caffeine also narrows brain blood vessels by blocking adenosine's vasodilation effect. This is why caffeine is included in headache medications like Anacin, as it alleviates vascular headaches by constricting blood vessels.

By inhibiting adenosine, caffeine boosts neuron activity in the brain. The pituitary gland interprets this surge as an emergency, prompting the release of hormones that stimulate adrenaline (epinephrine) production in the adrenal glands. Adrenaline, known as the "fight or flight" hormone, triggers several bodily responses:

This is why, after drinking a large coffee, you may experience cold hands, tense muscles, heightened alertness, and a noticeable increase in heart rate.