It’s a Tuesday after a long weekend and all I can think about is a large double shot coffee and how its magical caffeinated powers are going to get me through this long day! But then I got thinking further and wondering how caffeine actually does stimulate us and keep us awake! I did some research and here is a summary of what I found:
Caffeine works by changing the chemistry of the brain. It blocks the action of a natural brain chemical that is associated with sleep.
The chemical adenosine binds to adenosine receptors in the brain. The binding of adenosine causes drowsiness by slowing down nerve cell activity. In the brain, adenosine binding also causes blood vessels to dilate (presumably to let more oxygen in during sleep).
Adenosine is produced by your daily activity. For example, muscles produce adenosine as one of the by-products of exercise and is why exercise can be a good way to fight insomnia.
To a nerve cell, caffeine looks like adenosine. Caffeine, therefore, binds to the adenosine receptors. 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. 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 pressure rises
Blood flow to the stomach slows
The liver releases sugar into the bloodstream for extra energy
Muscles tighten up ready for action
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.
So there you go – there is a big science behind that cup of coffee and how it wakes you up! Though I must admit after reading this I think I will definitely be sticking to just one cup a day…