Blood alcohol content (BAC) is a measure used by doctors, medical examiners, and police officers, to determine an individual’s concentration of alcohol in the blood. A BAC of .30, for example, means that 3/10ths of 1% of someone’s blood volume (.003) is actually alcohol.
Alcohol is a substance that travels readily into the bloodstream. Alcohol is actually absorbed through the stomach lining into the system. So its effects are generally more immediate than other drugs that ingested orally.
Alcohol also crosses the blood/brain barrier much more readily than other substances. Something about the structure of the ethanol molecule allows it to permeate the entire human body in minutes. In the brain, its effects are powerful.
The occipital lobes, located in the back of the brain and responsible for visual perception, are soon bathed with alcohol, after a drink or more, and vision often blurs as a result. The equilibrium, located behind the ears, is thrown off, as the alcohol reaches it as well. This causes a person to struggle with balance and coordination. Thus, the highway patrol’s walk-the-line test is effective in rooting out those who have had too much to drink.
The prefrontal lobe, located behind the forehead, is the part of the human brain that makes us who we are. Containing our values, beliefs, aspirations, and wisdom, this part also gets an alcohol bath. Activity in this part of the brain is dulled accordingly, by the alcohol, and people behave impulsively, with reduced “inhibitions,” and at times, do things completely outside their value system.
The central nervous system is depressed by the alcohol, which is the most dangerous consideration in BAC, for the individual who is drinking. Usually, an individual will black out before he or she dies of too much of the central nervous system depressant, but at times they do not wake up, dying of alcohol poisoning.
The central nervous system controls the lungs, the heartbeat, and thus life itself. When too much alcohol is consumed, an individual can die of respiratory arrest (the lungs stop working), cardiac arrest (the heart stops working), or seizure (the brain stops working).
BAC is a measure that can determine if the cause of death was alcohol related, for a medical examiner. It can also determine if someone is a threat on the road, for a police officer. BAC is not a perfect science, but it is the best measure we have to determine how much alcohol an individual has consumed.