Caffeine is society’s favorite drug (legal or illegal). We consume it through coffee, tea, soda, and chocolate. Even some bugs, such as honeybees, seem to share our caffeine addiction, as they get a small dose from the nectar of certain flowers.
But why do we love this mysterious chemical so much? Sure, it’s found in products that are often laced with sugar, which has its own addictive qualities. But the main benefit that keeps us coming back is its ability to make us feel awake! In a world of busy schedules and endless responsibilities, we simply don’t have time to feel tired (although I am perpetually tired), which is why we turn to our favorite stimulant to help us take on our daily tasks.
But how does caffeine ‘wake up’ our brains?
A little brain chemistry 101
The answer to this question requires a brief science lesson. All of our thoughts, feelings, and actions are governed by our central nervous system, which is comprised of the brain and spinal cord (our peripheral nervous system includes the nerves that extend to all parts of our bodies). This system contains hundreds of billions of neurons (also known as nerve cells), which act as a communication network. For example, if your brain decides that you need to move your hand, it will send electrical and chemical signals along the path of connected neurons that lead to your hand, instructing it to move. Pretty nifty, huh?
The neuron structure
The image below is an example of a typical neuron, although their structure can vary.
The axon terminals of each neuron are connected to the dendrites of others, creating long complex chains of neurons. While we consider neurons to be connected to one another, there is actually a super tiny gap between the axon terminals and dendrites called the synapse. Between the cell body and terminal of the neuron is a long stemlike structure called an axon. The axon’s primary function is to carry electrical signals from one end of the neuron to the other, kind of like a wire.
The communication process
When a neuron receives a message, it passes an electrical signal down from the cell body through the axon. Once the signal reaches the axon terminals, it changes from electrical to chemical, by releasing groups of molecules called neurotransmitters into the synapse between the axon terminal and the dendrite of the adjacent neuron. The dendrite has receptors with specific shapes to match certain types of neurotransmitters. Once a receptor receives the neurotransmitter that fits just right, it communicates that neurotransmitter’s message via electrical signal down through the cell body and axon, and the cycle continues. The diagram below illustrates this process.
The types of neurotransmitters
There are all sorts of different neurotransmitters that act like little messengers carrying specific instructions from one neuron to another. Some of them, you’ve probably heard of, like dopamine, glutamate, or serotonin. The instructions carried by neurotransmitters can be summarized by three primary categories:
Excitatory – This basically means that the receiving neuron is being asked to continue sending the signal onto the next neuron.
Inhibitory – These types of neurotransmitters are essentially trying to slow down the neuron signaling process by telling the receiving neuron not to continue the signal to the next neuron.
Modulatory – Some neurotransmitters do a little bit of everything, meaning they have the ability to excite or inhibit neurons, and they can affect the behavior of other neurotransmitters. We call these modulatory.
What I’ve just described is a very basic overview of our nervous system’s communication process, but it’s important to note that there are many complexities involved in brain function that go far beyond this process. And now that I’ve potentially bored you with too much science talk, let’s get to the good part: how does caffeine get involved?
Caffeine: the sleepiness blocker
One of those neurotransmitters that we were just discussing is called adenosine. Adenosine naturally appears within the brain as we go about our day and is primarily inhibitory. As we exert ourselves and use energy, more adenosine builds up around our neurons and eventually finds its way to synaptic receptors. As an inhibitor, it will reduce the communication happening between neurons, essentially reducing brain activity.
What effect does all this adenosine have on you? It makes you tired! That’s right, adenosine plays a major role in promoting feelings of fatigue and increasing the urge to sleep. It’s kind of like your brain telling itself, okay, it’s time to power down so that we can recharge for a bit.
In comes our energy hero, caffeine! As it turns out, the structure of caffeine molecules is fairly similar to that of adenosine. So, when you drink that cup of coffee and introduce a bunch of caffeine molecules into your brain, they will find those receptors that were meant for adenosine and steal its spot. As caffeine takes up the receptor spots, adenosine is unable to carry out its role as an inhibitor. Essentially, caffeine blocks the natural process that tells our brain that it’s time to rest.
The brain fights back
If you are a regular consumer of caffeine, you may have noticed that your tolerance builds over time, requiring you to consume more caffeine just to maintain the same level of ‘awakeness’. It turns out there’s a reason for that.
Your brain, being the intelligent organ that it is, knows that adenosine plays an important role in making sure you get enough rest. So, when caffeine continues to get in the way by stealing adenosine’s receptor spots, the brain retaliates by creating more receptors for adenosine on the neuron dendrites. With more opportunities for adenosine to reduce brain activity (due to its inhibitory nature), you need to consume even more caffeine to take up all the additional adenosine receptor spots!
More fun facts about caffeine
Caffeine can temporarily increase your blood pressure and heart rate, which can contribute to the energetic feeling you get from consuming it.
According to the FDA, consuming more than 400 milligrams of caffeine a day (4 – 5 cups of coffee depending on caffeine concentration) may result in adverse health effects. Though people have varying sensitivities to caffeine.
It can take up to 12 hours for your body to completely process caffeine that you’ve consumed.
LAST WEEK’S QUIZ
You almost got it! The term “nutmeg” is commonly used in soccer. It’s when a player dribbles or passes the ball between a defender’s legs. As a defender that has been on the receiving end of a few, I can tell you that it’s quite embarrassing.
Love this - a good accompaniment to my case against caffeine but you do a great job of explaining how it works!
Eager to see which country consumes the most caffeine next week!