PHYSICAL TOLERANCE

Regular intake of alcohol causes an individual to gradually tolerate a substantial quantity in the blood. The brain gets used to alcohol. As a result, if you have drunk heavily for years, you may be able to look and behave normally even though your blood level would produce drunkenness in a person with a lower tolerance for alcohol. Heavy drinkers who have built up a physical tolerance to alcohol may talk coherently, but their ability to drive a car is still impaired and progressive damage to the brain, liver and other organs will still occur. 

A negative result of increased tolerance is that you become dependent on having a concentration of alcohol in your blood. Your gradually need to drink greater amounts to give you whatever effects you greater amounts to give you whatever effects you expect from drinking. This dependence degenerates into addiction and the greater levels of alcohol further damage the organs of your body including the brain.