Caffeine is bitter crystalline and is found in seeds, nuts or leaves of a number of plants in South America and East Africa. Coffee bean is well-known or main sources of caffeine. The beverages containing caffeine relieve or prevent drowsiness.

The main reason of caffeine us awake is that caffeine interrupts our daily sleeping patterns by altering the chemical reactionsin our brain. Caffeine increases nerve activity in our body keeping us alert and hyper active. The following activities happen after taking caffeine are given below-

1. It energize us by pumping the hormone adrenaline in our systems. Adrenaline is a hormone, which plays an important role in increasing blood flow to muscles, which also enhances output of the heart.
2. It increases dopamine levels in our body. Dopamine is an organic chemical that plays several important roles in the brain and the body.
3. It blocks the connection of adenosine to nerve cells. Adenosine is neuromodulator, which plays an important role in promoting sleep and suppressing arousal. It also plays in regulation of blood flow to various organs through vasodilation that is widening of blood cells. Caffeine bunds to adenosine receptor.

Thus, caffeine being a stimulant stays in our body for several hours keeping us awake enough to disrupt sleep.