It’s because of our old friends, the A2A receptors. Caffeine does just the opposite there, acting as a vasoconstrictor that causes blood vessels to contract and reducing blood flow. However, things work very differently in the brain. This apparent vasodilation is one of the reasons why medical experts say that coffee is good for heart health. There’s research showing that caffeine widens the blood vessels and increases blood flow in some parts of the body. The final important function of caffeine may seem to contradict what you’ve been told in the past. It also protects them from adenosine – until caffeine unbinds from the receptors and is metabolized by the body. It doesn’t just cause the release of hormones and neurotransmitters that energize us and make us feel happy. That’s why the caffeine in coffee or an energy drink makes us feel so good for a short time. But because caffeine blocks adenisone from attaching to the A2A receptors, it lets the surge of hormones course through the brain.
They also moderate levels of adrenaline, the so-called fight-or-flight hormone.Īs a stimulant, caffeine causes the release of serotonin, dopamine and adrenaline. They’re responsible for moderating the level of feel-good hormones and neurotransmitters, like serotonin and dopamine, released in the brain. Unlike A1 receptors, A2A receptors don’t have anything to do with getting tired. A2A Adenosine ReceptorsĪdenosine binds to A2A receptors in the brain, too. That’s why a cup of coffee only keeps you juiced for a few hours, and a 5-Hour Energy only keeps you juiced for, well, about five hours. Instead, the stimulant makes sure you’re not getting tired – until the effects of caffeine wear off. That prevents adenosine from binding to them and delivering its “you are getting very sleepy” message. It binds to the A1 receptors and blocks them. That’s part of the normal sleep-wake cycle.īut there’s one thing that can stop those “tiredness” messages from being delivered: caffeine.Ĭaffeine is able to act very much like adenosine, but it does so with a different purpose. After locking to some of them, the ones known as A1 receptors, adenosine sends messages throughout the brain and body to promote muscle relaxation and sleepiness. That’s why we get more and more tired as the day progresses the body’s levels of adenosine continually increase.Īdenosine delivers its signals by binding to groups of receptors in the brain called, as you’d probably guess, adenosine receptors. When we’re physically or mentally active, it produces more of them every hour.Īdenosine works like a neurotransmitter to carry signals throughout the brain – and one of the messages it carries is the need to rest. A1 Adenosine Receptorsĭuring the day, the body produces adenosine molecules. In this case, the most important chemical is known as adenosine. Just as with all other stimulants, caffeine’s secret is the way it interacts with important chemicals in the brain.
There’s no “magic ingredient” in caffeine that gives you its trademark jolt of energy. The natural and artificial forms of caffeine are chemically identical, so they work in exactly the same way. On the other hand, some of the caffeine now used in beverages like soda and energy drinks is man-made. Much of the caffeine we consume is natural, produced by and extracted from plants like the coffee plant (which, of course, produces coffee beans), the tea plant (Camellia sinensis) or the cacao plant (which produces the cocoa beans used to make chocolate). Here’s what it is: a stimulant that interacts with the central nervous system. Ask people what caffeine is, and you’ll get answers like “it wakes you up,” “it makes you more alert,” or “it boosts your energy.”īut those are actually examples of what caffeine does.
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