Caffeine is a naturally occurring chemical stimulant called trimethylxanthine. It can be addictive and debilitating as well as helpful, as both Bach and Beethoven, heavy coffee drinkers, would attest.
Caffeine stimulates the brain to produce the neurotransmitter dopamine by occupying the brain's adenosine receptors. Adenosine is what helps us feel like sleeping, but the adenosine receptors don't discriminate between adenosine and caffeine.

Dopamine elevates our moods to make us feel better and stave off depression, which is why there is so much coffee consumption in areas that lack sunshine for extended periods, such as the USA Pacific Northwest and Scandinavia. Dopamine also helps create motivation and contributes toward conscious body motion.

Some research even points to coffee drinkers having fewer problems with depression and Alzheimer's disease than non-coffee drinkers. While feeling better from the dopamine, the caffeine also increases the brain's activity and neuron firing.

This alerts the pituitary gland to release hormones that signal the adrenal glands to produce adrenaline (aka epinephrine) for "fight or flight." The adrenaline rush makes you more alert.

Adrenaline injections are sometimes administered to help overcome extreme breathing problems or cardiac issues. Caffeine can help get over an asthma attack by elevating one's mood, increasing heart rate, and dilating bronchial passages

source :naturalnews