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