How Does Coffee Work as a Stimulant in the Brain?

Coffee acts as a stimulant because caffeine blocks adenosine, an inhibitory neurotransmitter that binds to receptors and makes a person feel sleepy. The more adenosine that binds, the sleepier a person becomes. Caffeine occupies those receptors first, preventing adenosine from settling in and temporarily propping up alertness. Over time, the nervous system adapts, so the same cup produces a weaker effect, and some long-term drinkers report feeling sleepier rather than more awake.

Individual metabolism also shapes the response, which is why effects vary between people. Drinking coffee to stay awake is sometimes just a psychological ritual rather than a sign of coffee addicted dependence, and that distinction matters when judging whether a habit has crossed into addiction or withdrawal. The article separates this scientific boundary from ordinary routine and cites the FDA reference for safe intake, using simple analogies to explain the competition between adenosine and caffeine at the receptor level.

Why does coffee wake you up? What actually happens in the brain after you drink a cup? Many people find that after drinking coffee for a long time, its alerting effect is far less powerful than before, and they may even feel sleepier the more they drink. Behind this lies the competition between adenosine and caffeine at the receptor level, individual differences in metabolism, and adaptive changes in the nervous system. In addition, drinking coffee to stay awake is sometimes just a psychological ritual, which is a different matter from true caffeine addiction. This article will use simple analogies to break down the mechanism of caffeine, analyze the various reasons why its alerting effect fails, and clarify the scientific boundary between caffeine addiction and withdrawal reactions, while also providing the FDA reference for safe intake.

Why does a person feel refreshed after drinking a cup of coffee?

What exactly is the principle behind coffee's alerting effect?

Is this alerting effect really all thanks to caffeine?

(The typist is fleeing the interrogation scene...)

You may not know that every time you take a sip of coffee, a battle unfolds inside your brain. This little drama in the brain can be called

"Grab the couch!"

Venue : Your brain

Scene : The receptor couch area, which recognizes specific signaling substances.

Protagonist one: Adenosine, a bunch of lazy guys... These bros are an inhibitory neurotransmitter. Once the adenosine guys lie down on the couch (bind to receptors), you begin to feel sleepy~ The larger the adenosine crew, the more of them lie on the couch (bind to receptors), and the sleepier you become...

After you take a sip of coffee, the situation in your brain is roughly like this...

(The pink cushion plays the receptor, the cow cat plays caffeine, and the orange cat plays adenosine)

Protagonist two: Caffeine, a bunch of energetic lads... These bros are a central nervous system stimulant that can give you a brief boost in alertness. The caffeine guys mainly stop the adenosine guys from lying on the couch (prevent adenosine from binding normally to receptors), so they lie down on the couch as quickly as possible, one step ahead of the adenosine guys.

(Before you drink coffee): The adenosine guys drag their exhausted bodies around looking for a couch they can lie on (receptors)... At this point you do not feel sleepy, because the adenosine guys are still floating around (you only feel sleepy once the adenosine guys lie down!). Suddenly the adenosine guys shout, "Wow! A couch!" and flop onto it! Your sleepiness also begins to emerge...

"No, I need to drink coffee!"

After you gulp down a few mouthfuls of coffee, the caffeine guys make their entrance!

"Wow, so many lazy guys are approaching the couch?! No, we can't let them lie down! Brothers, hurry up, we have to get there before them, we can't let them lie down so easily!" So the caffeine guys, at flying speed, occupy as much of the couch area as possible or share the same couch with the adenosine guys (so that adenosine and receptors cannot bind normally).

If the adenosine guys have not yet swarmed onto the couch in full force, the appearance of the caffeine guys can indeed grab quite a few couches, and will also give you a brief period of alertness in the short term.

Then why does coffee sometimes make you sleepier the more you drink it??!!

There are three possibilities!

In some cases, the adenosine guys have already swarmed in and comfortably lain down on the couch, and the caffeine guys cannot pull away those adenosine bodies whose butts are already stuck firmly to the couch... (You drank too late. Once adenosine and receptors have already bound, it is meaningless for caffeine to try to stop them.)

In some cases, because your own metabolism is fast, the caffeine guys disappear before they have grabbed many couches... But their appearance may also stimulate more adenosine guys to show up... And then? Then of course they lie on the couch! (Some people are naturally strong metabolizers, so caffeine's duration is shorter, and therefore caffeine cannot produce much of an alerting effect, while it may even increase your sleepiness.)

In some cases, the adenosine guys get used to the presence of the caffeine guys, and always find a way to lie steadily on the couch when the caffeine guys arrive! Facing a bunch of adenosine guys who are not worried at all about the caffeine guys suddenly arriving and are already dead asleep, the caffeine guys are helpless too (if you drink coffee often, the nervous system develops antibodies to caffeine, blocking caffeine's alerting effect.)

Therefore, for people who do not drink coffee often, caffeine intake may make them much more alert; but for people who drink coffee long term, caffeine may not have the same effect on them.

"No way! I drink coffee every day, and it still wakes me up!"

This may be a kind of "ritualized anesthesia," an illusion that coffee wakes you up!

Ritualized inebriation first appeared among people who drink alcohol. Drinking is not necessarily about getting dead drunk; more often, alcohol gives oneself a certain sense of ritual , and then one goes to do something one would not usually dare to do. In plain terms, it is "liquid courage." Coffee is the same, equivalent to giving yourself a "trigger" to start a new day full of energy.

Anthropology researcher Krystal D'Costa once wrote in Scientific American: We live in an era that demands efficiency at every moment. As a mental stimulant, coffee has become the thing we理所当然 want to choose when we feel inefficient and low on energy. We hope it can quickly enter the brain through the bloodstream, helping us still muster energy, stay alert and focused, and maintain work efficiency when we are not at our best.

Therefore, for people who drink little coffee, drinking coffee can make them "more alert"; for people who drink coffee often, drinking coffee can make them "restore alertness."

Then does the above-mentioned "ritualized anesthesia" count as caffeine addiction?

No! These are two different things!!

"Ritualized anesthesia" affects the mind, while excessive caffeine intake leading to addiction/severe dependence on caffeine affects both mind & body. The reason humans become addicted to caffeine is that caffeine mimics cocaine and cannabis in the reactions it produces in our brains, stimulating abnormal secretion of the neurotransmitter dopamine in the synaptic cleft. Over time, excessive caffeine intake will cause symptoms of caffeine addiction in the body.

After caffeine addiction, one will face withdrawal reactions, meaning a special psychological syndrome that appears after stopping caffeine intake or reducing the dose. For example, there may be lethargy, low mood, restlessness, nervousness, and adverse reactions in the gastrointestinal/urinary/cardiac systems that affect daily life. Generally speaking, the symptom of caffeine addiction only occurs in people who have consumed caffeine products long term and in excess.

But everyone can tolerate a different amount of caffeine! If we go by the safe intake standard given by the FDA (U.S. Food and Drug Administration), as long as you do not consume more than 400 mg of caffeine per day long term (a 225 ml pour-over coffee brewed from 15 g of coffee at a 1:15 coffee-to-water ratio contains about 60-90 mg of caffeine, that is, 4-5 cups of pour-over coffee), caffeine addiction generally will not occur.

"Coffee is delicious, but remember not to overdo it!!!!" If you really feel very tired, what you should do is pay more attention to your mental/physical condition, and not rely excessively on coffee to stay alert~

Image source: Internet

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The above content is compiled by CoffeeHunters, a coffee news website.