The brain is the control center of the human body, influencing everything from memory to coordination. As alcohol enters the bloodstream, the brain becomes unable to function normally, and thus the body cannot operate as usual. Based on the number of drinks and the blood-alcohol level of the drinker, there is a predictable process of alcohol-induced brain dysfunction.

Step 1
The frontal lobe of the brain is the first area to be affected by alcohol. After one or two drinks, the blood-alcohol level is between 0.01 and 0.10 - surpassing the legal limit of 0.08 - and reason and inhibition are impaired. This means the drinker might do things he or she would not normally do. A now uninhibited high school student may engage in violent behavior, sexual activity or drug use.

Step 2
The parietal lobe of the brain is the next area to be affected after three or four drinks, when the blood-alcohol level is between 0.10 and 0.30. The parietal lobe is responsible for sensory control of the body. At this phase, a drinker may experience slurred speech unsteady gait and loss of motor skills. At this stage, a high, school student may believe he or she tan drive, but will have slowed reflexes and poor judgment.

Step 3
Following five or six drinks, the blood-alcohol level in the drinker is more than twice that of the legal limit, between 0.20 and 0.30. At this stage, the vision of the drinker becomes affected. A loss of color and distance perception, in addition to seeing double and having distorted vision, are the common symptoms at this stage, when the occipital lobe is affected.

Step 4
After the seventh and eighth drinks, or when the drinker's blood-alcohol level is between 0.15 and 0.35, the cerebellum - the coordination center of the brain - is affected. At this stage equilibrium is lost, and the drinker will have difficulty walking.

Step 5
Finally, after 10 or more drinks, when the blood alcohol level is between 0.25 and 0.50, the thalamus and medulla are affected by alcohol, causing the vital centers of the body to shut down. The respiratory center is depressed, and the drinker will not breathe at an adequate rate and volume to maintain consciousness. Additionally, temperature regulation is impaired, and the drinker is unable to maintain a normal body temperature.
The circulatory system is also regulated by the thalamus and medulla, and at blood-alcohol levels of 0.25 and 0.50, a stupor is achieved, which may lead to shock and death.
Often at this blood-alcohol level, the drinker is unconscious when he or she vomits and subsequently will inhale the vomit into the lungs, a condition called aspiration pneuminitis that is almost always fatal.

Reference: "A Summary of Facts on Alcohol" brochure by G.C. Sconce