Caffeine & Nerves

Caffeine is a bitter alkaloid found in several plants, where it serves as a deterrent to predatory insects. In effect, this substance is a natural pesticide that immobilizes and even kills certain insects after feeding on the leaves of its host. You probably associate caffeine with coffee, the hot beverage made from the roasted, ground beans of Coffea arabica. However, caffeine is also abundant in some herbs, seeds and nuts. What you may not realize is that caffeine is a drug, a psychoactive stimulant to be exact. This means that it targets the central nervous system and affects cognitive function, mood and behavior.

Sources

Aside from the cup of java you may enjoy each morning, other sources of caffeine include cola, cocoa, yerba mate, guarana and tea. Since cocoa is included in this list, chocolate is a caffeinated food because it contains cocoa powder. Incidentally, tea means an infusion made from the leaves of Camellia sinensis, which all black, red, white and green teas come from. Herbal teas, such as chamomile or mint tea, are not true teas and do not contain caffeine.

Metabolism

Caffeine is an antagonist of adenosine, a neurotransmitter involved in promoting sleep. If you drink coffee on a regular basis, your body responds by making more adenosine receptors. Although this is a clever maneuver on the part of the central nervous system to help the body cope with the biological effects of caffeine, it also sets up a scenario for addiction. At first, an event called tolerance adaptation occurs, in which a level of tolerance to caffeine is allowed to negate the stimulatory effects of the drug. In a 2000 review published by the American College of Neuropsychopharmacology, Roland R. Griffiths and Geoffrey K. Mumford report that it's possible to achieve complete tolerance of caffeine within a week, assuming you drink several cups of coffee per day. If you then reduce your caffeine intake, you become more sensitive to the effects of adenosine, which causes you to experience symptoms of withdrawal.

Central Nervous System Effects

Several undesirable effects can occur from heavy caffeine consumption, often collectively referred to as "the jitters." Literally, caffeine can make the nerves in your muscles twitch. Blood pressure, regulated to a degree by adenosine, may increase. Like other stimulant drugs, caffeine can produce nervousness, anxiety, irritability and rapid heart beat. These symptoms characterize a medical condition called caffeinism, which may also be responsible for pain, cramps and twitching associated with Restless Legs Syndrome.

Sympathetic Nervous System Effects

Caffeine stimulates an increased production of catecholamines, adrenal hormones responsible for the "fight or flight" response. You might be familiar with the effects of one of the most abundant catecholamines produced by the adrenal glands: adrenaline. Other catecholamines include norepinephrine, also known as noradrenaline. Caffeine increases the release of these agents from nerve endings.