Many of us rely on a cup of coffee or tea to wake up in the morning. Sip after sip, we begin to feel more alert, focused, happy, and energetic, despite a poor night's sleep. Caffeine's effects on the brain are due to the stimulant's ability to block molecules that induce sleep.

In the TED-Ed video, "How does caffeine keep us awake?" Hanan Qasim explains the world's most popular stimulant keeps us alert by blocking the substance adenosine. This substance docks to neuron receptors that are tailored to the high-energy molecule, ATP, causing a cascade of biochemical reactions that make neurons fire more sluggishly and slow the release of important brain-signaling molecules. In other words, adenosine works to make us sleepy.

Read More: Brain On Caffeine Has Its Positives And Negatives

Caffeine, known as an adenosine receptor antagonist, works by derailing this process via blocking adenosine. Caffeine and adenosine have a similar enough molecular structure that caffeine can wedge into adenosine receptors, but not close enough to activate them. Adenosine works to inhibit neurons, while caffeine inhibits the inhibitor in order to stimulate us.

Often times, when we have coffee, tea, or even soda, we can feel a surge of energy and positive emotions. In some neurons, adenosine receptors are linked to dopamine receptors, a molecule in the brain that functions to promote feelings of pleasure. When adenosine docks in one of these paired receptors, it makes it difficult for dopamine to stay in its own spot, which can lead to decreased moods.

But, when caffeine replaces adenosine, dopamine can slide in its spot, which promotes alertness and positive moods. However, this sudden surge can lead to an increase in heart rate and blood pressure; increase in urination or diarrhea; and contribute to insomnia and anxiety. This is because caffeine acts as a stimulant in the central nervous system with its effects beginning as early as 15 minutes after ingestion and last up to six hours, according to Michigan University Health Service.

The brain can readily adapt to the regular consumption of caffeine. This can lead adenosine receptors to be perpetually clogged and cause the body to manufacture extra ones. This means, even if caffeine is lurking in the brain, adenosine can still function by signaling the brain to power on.

The presence of extra adenosine receptors explains why we need to consume more and more caffeine to stay alert. Contrastingly, quitting caffeine promotes symptoms of withdrawal, as there are plenty of adenosine receptors, but no competition. This makes adenosine work overtime, causing symptoms like headaches, tiredness, and depressed moods. In a few days, the extra adenosine receptors will disappear, and the body will readjust back to normal without caffeine.

Overall, caffeine works by changing the brain chemistry, and blocking adenosine, the natural brain sleep-inducing chemical. It is through this process that we experience bouts of alertness and bouts of sleepiness when we either drink too much caffeine or not enough. So, if we rely on coffee during the day, we need to start monitoring your intake if we begin having trouble falling asleep at night.

See Also:

Caffeine Can Make Driving Safer by Maintaining Driver's Alertness

4 Effects Of Drinking Too Much Coffee You Probably Have Never Heard Of