The pharmacodynamic properties of alcohol classify it as a central nervous system depressant. The more alcohol you consumed the greater its effects. Alcohol impairs both cognition (the process of knowing, thinking, learning and judging) and psychomotor skills (voluntary movement). If you think of the evolution of the brain, the affects of alcohol are felt by the most recently developed parts of the brain. These parts of the brain are responsible for judgment, inhibition, personality, intellectual and emotional states. If you continue to drink, your psychomotor functions such as muscular coordination, balance, eye movement, etc. will be impaired. Continue to drink and involuntary movement, such as respiration, is affected, leading to possible coma or death by alcohol poisoning.
Law enforcement relies on tasks requiring divided attention skills as these are specifically sensitive to alcohol. The Committee on Alcohol and Other Drugs of the National Safety Council concluded that all individuals are impaired with respect to operating a motor vehicle at alcohol concentrations of 0.08 and above, while some individuals are impaired with respect to driving at concentrations below 0.08. Interestingly, the impairment at this level has only been scientifically correlated to performance on the standardized field sobriety tests by one questionable study. HERE For a critique of the science behind the standardized field sobriety tests, check HERE.
Alcohol elimination occurs through metabolism, excretion and evaporation. Metabolism accounts for approximately 95% of elimination. Enzymes act on alcohol molecules to change them into other compounds; these by-products are further metabolized. Alcohol dehydrogenase (ADH) in the liver is the enzyme that is primarily responsible for alcohol metabolism. ADH is also located in the stomach lining, causing a small portion of an alcohol dose to be eliminated before it has a chance to be absorbed. The average rate of elimination (combining metabolism, excretion and evaporation) is between 0.015 to 0.018% per hour.
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