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Caffeine and the Central Nervous System

Apr 18, 2011 | By Louise Tremblay

Your central nervous system, an organ system made up of your brain and spinal cord, reacts to certain chemicals from your diet. Among these chemicals is caffeine, a drug found in a variety of foods and beverages including coffee, black and green tea, energy drinks, cola, chocolate and some fruits such as guarana berries. Once ingested, caffeine enters your brain and temporarily affects your central nervous system, since caffeine molecules can interact with cells in your brain.

Caffeine and Brain Signaling

Caffeine affects your brain chemistry by binding to proteins called adenosine receptors. Normally, these proteins detect adenosine in your brain, and in the presence of the chemical, induce a feeling of drowsiness. When caffeine binds to these adenosine receptors, it prevents your brain cells from sensing and binding to adenosine, explains Eric Chudler, Ph.D., research associate professor at the University of Washington. Since adenosine can normally help trigger a feeling of drowsiness, caffeine blocking adenosine signals helps promote alertness. Caffeine also stimulates regions of your brain that control other physiological processes, such as heart rate, and exposure to caffeine can increase your heart rate.

Positive Effects of Caffeine

Since caffeine can reduce drowsiness, drinking caffeine can help you stay awake for long periods of time to work. Consuming caffeine can temporarily improve your mental ability to increase your studying or work productivity, helping you perform complex mental tasks. Caffeine can also increase your reflexes and athletic performance, even when you are fatigued, according to a study published in "Medicine and Science in Sports and Exercise" in January 2011.

Negative Side Effects

Despite its numerous benefits, caffeine's effect on your brain chemistry can also prove harmful to your health. Consuming large amounts of caffeine can overstimulate your sympathetic nervous system -- the part of your nervous system that helps your body respond to stress -- leading to side effects including an increased heart rate and blood pressure and possible difficulties sleeping. As the caffeine wears off, caffeine withdrawal can also affect your nervous system, causing headaches, irritability and drowsiness, according to the University of Maryland Medical Center. Consume caffeine in moderation: Limit your intake to around 250 mg daily, the equivalent of about 2.5 cups of coffee or around 4 shots of espresso.

Additional Risks and Considerations

While the side effects of caffeine may prove temporarily discomforting for many people, some individuals may face an additional risk upon consuming large amounts of caffeine. If you suffer from hypertension -- high blood pressure -- consuming caffeine may worsen your condition, so you should consult your doctor before consuming foods or drinks containing the chemical. In addition, the Linus Pauling Institute at Oregon State University warns that pregnant women, or women trying to become pregnant, should not exceed 300 mg of caffeine daily.

References

Article reviewed by S.C. Ville Last updated on: Apr 18, 2011

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