MCQ Detailed View

Blood alcohol concentration (BAC) is the measure of the amount of ethanol (alcohol) present in the blood. It is usually expressed as a percentage, meaning grams of alcohol per 100 milliliters of blood. Even small amounts of alcohol can affect the human brain and nervous system, but very high levels can become life-threatening.

At a BAC of around 0.02 to 0.05, a person may feel relaxed, with mild loss of judgment. As the level increases to 0.08, reaction time and coordination are impaired, which is why most countries set this as the legal driving limit. At 0.15 to 0.25, severe impairment of balance, vision, and motor control occurs. The person may become confused, unable to walk properly, and risk falling unconscious.

When the blood alcohol level rises to about 0.30, the person may lose consciousness completely. At this stage, breathing and heart function start to slow down dangerously. If the BAC reaches 0.41 or higher, it is often fatal, because the alcohol depresses the central nervous system to the point that vital functions like breathing, heart rate, and body temperature regulation can stop. This is called respiratory depression or alcohol poisoning.

The exact fatal dose can vary depending on age, weight, tolerance, and individual health conditions. However, medical studies and clinical evidence confirm that 0.41 BAC and above is associated with a very high risk of death. That is why this level is considered lethal in biology and medicine.

Understanding BAC is important not only in biology but also in health sciences and public awareness. Alcohol’s effect on the human body is a major topic in physiology, as it directly impacts the brain, liver, and cardiovascular system.