Remember the nights during exams? How a single cup of hot coffee used to keep you up all night with your books or the time when you need to complete a presentation for office. The only thing that comes to your mind for keeping your sleep away is coffee.
But how coffee keeps us awake?
Coffee’s ability to keep you awake is all thanks to its primary constituent – caffeine.Caffeine is trimethylxanthine(C8H10N4O2).
Caffeine occurs naturally in a number of plants, including coffee beans. Your average 6-ounce cup of drip-brewed coffee contains 100 mg of caffeine. A 12-ounce cola soft drink contains about 50 mg of caffeine. It’s an addictive stimulant drug that operates in the brain the same way cocaine and heroin do (although caffeine is much milder than those drugs).
Caffeine works by changing the chemistry of the brain. It blocks the action of a natural brain chemical that is associated with sleep. (Now here also comes chemistry- subject which haunts many students)
So first we should start with how sleep sets in?
Drowsiness is caused by the slowing down of nerve cell activity in your brain. A chemical called adenosine binds itself to the adenosine receptors in our brain. It is this binding of adenosine that causes the slowing down of nerve cell activity. Where does Adenosine come from? It is produced by your daily activity. For example, muscles produce adenosine as one of the by-products of exercise. So in short sleep is a natural process of your daily life.
How caffeine prevents sleep?
Here is the amazing fact about caffeine that makes it so effective against sleep: To a nerve cell, caffeine looks like adenosine!
Therefore the adenosine receptors bind to the Caffeine in your coffee, instead of the actual adenosine. However, it doesn’t slow down the cell’s activity as adenosine would. The cells cannot sense adenosine anymore because caffeine is taking up all the receptors adenosine binds to. So instead of slowing down because of the adenosine level, the cells speed up!
With caffeine blocking the adenosine, you have increased neuron firing in the brain. The pituitary gland sees all of the activity and thinks some sort of emergency must be occurring, so it releases hormones that tell the adrenal glands to produce adrenaline (epinephrine). Adrenaline is, of course, the “fight or flight” hormone and it has a number of effects on your body:
- Your pupils dilate
- Your breathing tubes open up
- Your heart beats faster
- Blood vessels on the surface constrict to slow blood flow from cuts and also to increase blood flow to muscles
- Blood flow to the stomach slows
- The liver releases sugar into the bloodstream for extra energy
- Muscles tighten up ready for action
In short, it banishes drowsiness and gets you all charged up. This explains why, after consuming a big cup of coffee, your hands get cold, your muscles tense up, you feel excited and you can feel your heart beat increasing.