When you drink a cup of coffee, it contains a drug named caffeine which takes effect on your body minutes from the start of consumption. It blocks chemical signals that pass through your brain, thus stopping you from feeling tired. In moderate proportions caffeine can improve you mental ability, reaction times, memory and reasoning skills. It takes your body three to five hours to break down the caffeine, which is the answer to why coffee near bed time will not help you sleep.
Caffeine is as addictive as nicotine. Even if you only drink one large coffee per day (or three cans of cola) you may feel the ill side effects of missing a dose when you do not drink this for a day, as with coming off prescription drugs and the same for smokers trying to quit, it is the same thing. Withdrawal symptoms from caffeine can include but is not limited to headaches, drowsiness and loss of concentration. Drinking coffee will relieve these symptoms, so it can become one vicious cycle.
Also caffeine in high doses can make the average person very anxious, but in vulnerable people one cup of filter coffee can result in similar symptoms to panic attacks.
To a nerve cell, caffeine looks like adenosine: Caffeine binds to the adenosine receptor. However, caffeine doesn’t 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 like Anacin contain caffeine — constricting blood vessels in the brain can help stop a vascular headache. Go to http://www.lifehacker.com.au/2010/07/what-caffeine-actually-does-to-your-brain/ for more updates.
Caffeine’s effect on the brain causes increased neuron firing. The pituitary gland senses this and takes a form of emergency action because it thinks an emergency itself is occurring in your brain. So in turn it releases hormones that tell the adrenal glands to produce adrenaline. Adrenaline is the fighting hormone and it has a number of effects on your body both physically and mentally;
1 Your pupils dilate.
2 The airway opens up.
3 Your heart beats faster.
4 Blood vessels on the surface constrict to slow blood flow from cuts and increase blood flow to the muscles.
5 Blood pressure rises.
6 Blood flow to the stomach slows.
7 The liver releases sugar into the bloodstream for extra energy.
8 Muscles tighten up, ready for action.
This explains why, after consuming a big cup of coffee, your hands get cold, you muscles grow tense, you get excited and your heart beats faster. For more detailed information check this link here for more reviews.