Worldwide, people consume an estimated 10 billion pounds of coffee every year, per the the Encyclopedia of Mental Health Disorders website. There is more caffeine in coffee than in soft drinks, cocoa and tea. Caffeine affects the brain by increasing attention, alertness and energy, but it also affects the heart.
Caffeine
Caffeine is a stimulant and is referred to as a psychoactive drug because it can affect the behavior and the mind. It is, in fact, the number one psychoactive drug used by people throughout the world, according to Charles O'Brien, professor of psychiatry at the University of Pennsylvania School of Medicine, in the book "Goodman & Gilman's The Pharmacological Basis of Therapeutics." It is an ingredient in soft drinks, cocoa, tea and coffee, as well as in many prescriptions and over-the-counter drugs.
Effects of Caffeine
Once caffeine is absorbed into the bloodstream, it is quickly distributed throughout the tissues of the body and can even cross the placenta to reach the fetus of a pregnant woman. Caffeine has several effects. It increases the activity of the nerves in the brain, energy, attention and alertness. It also increases the amount of water that people lose in their urine, can make them breathe faster and increases blood pressure and heart rate.
Hypothesis About Caffeine and Heart Rate
Chemically, caffeine is a methylxanthine drug and pharmacologists have several hypotheses about how this type of drug works. One hypothesis is that it interferes with a particular protein that results in a high concentration of a substance called cyclic AMP, as explained in "Basic & Clinical Pharmacology" by Homer Boushey, M.D., professor of medicine at the University of California at San Francisco. A high amount of cyclic AMP can have various effects, including relaxing the smooth muscles, lowering the immune system activity of certain cells and raising the heart rate.
Second Hypothesis
Eric Chudler, Ph.D. of the University of Washington explains another hypothesis about how caffeine affects the heart rate. In this hypothesis, caffeine relaxes the airways, tightens the blood vessels and raises the heart rate because it stops a substance called adenosine from attaching to cells within the brain and in areas throughout the body. Adenosine slows down the activity of the cells; when caffeine attaches, it makes the nerve cells work faster. This, in turn, makes the pituitary gland in the brain release a hormone that increases the heart rate.
References
- "Basic & Clinical Pharmacology"; Bertram Katzung, M.D., et al..; 2009
- "Current Medical Diagnosis & Treatment 2011"; Stephen McPhee, et al.; 2011
- "Goodman & Gilman's The Pharmacological Basis of Therapeutics"; Laurence Brunton, Ph.D.; 2006
- University of Washington: Effects of Caffeine on the Nervous System
- Encyclopedia of Mental Health Disorders: Caffeine-Related Disorders
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