a library of information on how to mix exotic drinks, they could find little about what happens after the drinking starts. The person who wants to drink responsible y must know the short-term and long-term effects of alcohol on the body. Those who want to understand the social custom of drinking, problem drinking, and alcoholism must also know these effects. SHORT-TERM EFFECTS. –Most people drink alcoholic beverages to get feelings of pleasure as well as to relieve tension. No doubt that is the reason for the popularity of alcohol as a social beverage. Drinking has become such a familiar part of our society that we do not think of alcohol as a drug. However, it is as much a drug as one prescribed in carefully regulated dosages by a physician. Alcohol affects the whole body through the central nervous system–the brain. Alcohol does not act directly on the tongue or legs to cause the familiar signs of slurred speech and an unsteady gait connected with drunkenness. Instead, it affects the parts of the brain that control those parts of the body. Alcohol can act as a stimulant at low doses and as a brain depressant at higher doses. The speed with which alcohol brings on drunkenness and drunken behavior depends upon the rate of its absorption into the bloodstream and a person's tolerance for alcohol. Although the body must digest food before it can enter the bloodstream, it does not have to digest alcohol. Alcohol immediately passes directly through the wall of the stomach and small intestines into the bloodstream. Then the blood rapidly carries it to the brain. Even the first few sips of an alcoholic beverage may cause changes in mood and behavior. These changes may be influenced by what the person has learned to expect from previous drink experiences. Alcohol is metabolized (burned and broken down) in the body at a fairly constant rate. As a person drinks faster than the alcohol can be burned, the drug accumulates in the body. That results in higher and higher levels of alcohol in the blood. BLOOD-ALCOHOL LEVELS AND BEHAVIOR. –The first consistent changes in mood and behavior  appear  at  blood-alcohol  levels  of approximately 0.05 percent; that is, 1 part alcohol to 2,000 parts blood. That level would result if a 150-pound person took two drinks in succession. A blood-alcohol level of 0.05 percent can affect a person’s thought, judgment, and restraint and cause the person to feel carefree. The person feels a release from many ordinary tensions and inhibitions; in other words, the person loosens up. Most people drink in moderation mainly to achieve this relaxed state. As more alcohol enters the blood, the depressant action of alcohol involves more functions of the brain. At a level of 0.10 percent (1 part to 1,000), voluntary motor actions-hand and arm movements, walking, and sometimes speech-become clumsy. A level of 0.20 percent (1 part to 500) measurably impairs the controls of the entire motor area of the brain as well as that part of the brain that guides emotional behavior. At this stage the person will stagger and may want to lie down. The person may also become easily angered, may become boisterous, or may weep. The person is drunk. A concentration of 0.30 percent (1 part to 300) dulls the person’s response to stimulus and understanding controlled by the deeper areas of the brain. At this level a person may be confused or may lapse into a stupor. Although aware of surrounding sights and sounds, the person has poor understanding of what he or she sees or hears. With 0.40 to 0.50 percent alcohol in the blood (1 part to 250 or 200), the person becomes unconscious and may go into a coma. Still higher levels of alcohol block the center portions of the lower brain that control breathing and heartbeat, causing death to occur. This progression of effects is not unique to alcohol. Other hypnotic-sedative drugs, such as barbiturates, ether, and chloral hydrate, can also produce this progression of effects. Blood-alcohol  levels  have  important  legal implications. In most states, a person with a blood-alcohol level of 0.05 percent or less is legally presumed sober and in condition to drive a motor vehicle. However, in some states, a person with a level of 0.10 percent or 0.08 percent is legally presumed intoxicated or under the influence; in others, the 0.15-percent level means legal impairment. CHRONIC HEAVY DRINKING. –Drinking large amounts of alcohol for an extended length of time reduces the brain’s sensitivity to the alcohol. Therefore, a person must drink greater amounts of alcohol to feel its effects. This change in the sensitivity of the brain is called tolerance. Increased tolerance is a symptom of all chronic users of addictive drugs and is believed to be the basis of addiction or dependence. 3-16