Coffee is as much a part of the morning ritual as brushing your teeth and making the bed. According to its adherents, it can alternately keep you calm, sharpen your mind, or provide the vital boost to make it through an all-nighter.
Caffeine is a natural component of chocolate, coffee, and tea, and is added to colas and energy drinks. The international medical community recognizes caffeine withdrawal as a medical syndrome; yet, it is a common ingredient in diet pills and some over-the-counter pain relievers and medicines, and it is being studied for its potential benefits in battling Parkinson’s disease, Alzheimer’s, and even cancer.
The “caffeine” term is the commercial name for a naturally occurring chemical stimulant called “tri-methylxanthine”. It is a drug, and actually shares a number of traits with more notorious drugs.
The brain chemical responsible for sleeping is called “adenosine”; as adenosine is created in the brain, it binds to adenosine receptors. This binding causes drowsiness by slowing down nerve cell activity; in the brain, this also causes blood vessels to dilate, most likely to let more oxygen into that organ during sleep. To a nerve cell, caffeine looks exactly like adenosine and so caffeine automatically binds to the adenosine receptor; however, caffeine does not slow down the cell’s activity like adenosine would.
As a result, the cell can no longer identify adenosine because caffeine is taking up all the receptors that adenosine would normally bind to. Instead of slowing down because of the adenosine’s effect, the nerve cells speed up. Caffeine also causes the brain’s blood vessels to constrict, because it blocks adenosine’s ability to open them up. This effect is why some headache medicines constricting blood vessels in the brain can help stop a vascular headache.
Today, caffeine is used much as it has always been for generations; it provides a “boost of energy” or a feeling of heightened alertness. Many students can recall using strong coffee or caffeine pills to stay awake while cramming for finals. Likewise, drivers on long road trips often fill their cup holders with energy drinks or convenience-store coffees to help them push through to their destinations.
References
http://health.howstuffworks.com
http://coffeetea.about.com