How Caffeine Works

Ray Williamson Posted on: 2014-04-21 12:00 AM

 
Have you ever wondered why after a cup of coffee why you feel alert charged and can even have a feeling of excitement?  Well caffeine affects your brain chemistry by competing with chemical Adenosine which is one of the chemicals your body needs to make you sleep. 
 
Adenosine binds to receptors in the brain that cause nerve cell activity to slow down and blood vessels  to dilate lowering your blood pressure and possibly allowing more oxygen into your blood during sleep.
 
Caffeine readily crosses the blood–Brain barrier that separates the bloodstream from the interior of the brain. Once in the brain, the principal mode of action is as a nonselective antagonist of adenosine receptors. The caffeine molecule is structurally similar to adenosine, and binds to adenosine receptors on the surface of cells without activating them (an "antagonist" mechanism of action). Therefore, caffeine acts as a competitive inhibitor.  
The result is that instead of slowing the body down the cells speed up. Caffeine causes the brains blood vessels to constrict because there is no adenosine to dilate them. Caffeine can even help relieve vascular headaches but that will be another post.
 
Now that the adenosine is being blocked there is increased neuron firing in the brain. The pituitary gland sees all of the additional activity in the brain and responds as though there is some sort of emergency by releasing adrenaline. 

The adrenaline causes:

• 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

 
Your liver will breakdown caffeine in a healthy adult at rate of ½ of the caffeine in your blood stream ever 5- 6 hours, referred to as the half life. This is why that third cup of coffee in the day doesn’t give you the same buzz because your body still has ½ of the caffeine from the first cup and even more from the second cup still in your system.  Pregnant women and people with impaired liver function can expect caffeine to remain active the blood for much longer. 

Because Caffeine is a drug your body develops a tolerance to it by increasing the production of and the sensitivity to adenosine.  That is why heavy coffee drinkers are known to shamble around like zombies until because there is excess adenosine making you drowsy and the excess caffeine kept you from a good nights sleep. Your body needs that first cup to get the balance right.