<div class="quote_poster">Laker_fan Wrote</div><div class="quote_post">Wow, I never realised there were so many coffee addicts around! Personally, I'm not a big fan of coffee, I don't really need it to keep me focused in the mornings. Instead, I just wait a couple of hours until I'm fully out of my sleep. Does coffee really work? I didn't realise it makes your heart beat faster etc... It does nothing for me. I drink it like once every 3 months.</div> I'm pretty sure Coffee works (makes people less sleepy, adds adrenaline to bloodstream, etc). I found this article informative. <div class="quote_poster">Quote:</div><div class="quote_post">In the HowStuffWorks article How Sleep Works, the action of adenosine is discussed. As adenosine is created in the brain, it binds to adenosine receptors. 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). To a nerve cell, caffeine looks like adenosine. Caffeine therefore binds to the adenosine receptor. However, it doesn't slow down the cell's activity like adenosine would. So the cell cannot "see" 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. You can see that 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 like Anacin contain caffeine -- if you have a vascular headache, the caffeine will close down the blood vessels and relieve it. So now 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 the "fight or flight" hormone, and it has a number of effects on your body: * Your pupils dilate. * Your breathing tubes open up (this is why people suffering from severe asthma attacks are sometimes injected with epinephrine). * 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.</div> http://home.howstuffworks.com/caffeine3.htm <div class="quote_poster">Quote:</div><div class="quote_post">Caffeine also increases dopamine levels in the same way that amphetamines do (heroine and cocaine also manipulate dopamine levels by slowing down the rate of dopamine re-uptake). Dopamine is a neurotransmitter that, in certain parts of the brain, activates the pleasure center. Obviously, caffeine's effect is much lower than heroin's, but it is the same mechanism. It is suspected that the dopamine connection contributes to caffeine addiction.</div> <div class="quote_poster">Quote:</div><div class="quote_post">The most important long-term problem is the effect that caffeine has on sleep. Adenosine reception is important to sleep, and especially to deep sleep. The half-life of caffeine in your body is about 6 hours. That means that if you consume a big cup of coffee with 200 mg of caffeine in it at 3:00 PM, by 9:00 PM about 100 mg of that caffeine is still in your system. You may be able to fall asleep, but your body probably will miss out on the benefits of deep sleep. That deficit adds up fast. The next day you feel worse, so you need caffeine as soon as you get out of bed. The cycle continues day after day. This is why 90% of Americans consume caffeine every day... </div> http://home.howstuffworks.com/caffeine4.htm
