Final answer:
Alcohol affects consciousness by inducing euphoria at low doses and sedation at higher doses. It also impairs cognitive functions like reaction times and memory, and can lead to a complete loss of consciousness with excessive use.
Step-by-step explanation:
Alcohol is classified as a depressant, affecting consciousness in various ways. One effect is the induction of feelings of euphoria at low doses. However, as the alcohol consumption increases, it can lead to sedation. Alcohol is associated with decreased reaction times, impaired visual acuity, reduced alertness, and a lack of behavioral control. With excessive alcohol use, an individual might experience memory loss or even a loss of consciousness. Notably, the use of alcohol during pregnancy can result in fetal alcohol spectrum disorder (FASD) or fetal alcohol syndrome (FAS) in the infant.