What makes you feel drunk?

Alcohol is a mood altering substance. It affects the nerves that pass messages around the body by slowing them down, and the more you drink the greater the effect. The reason people often get more lively when they've had a drink is that alcohol affects parts of the brain responsible for self-control. As you drink, the alcohol passes into your bloodstream. 

Ethanol is the intoxicating part of alcohol and its molecules are so small that they can actually pass into the gaps between brain cells.  There it can interfere with the neurotransmitters that enable all the brain’s activities.  If you drink fast, alcohol will start to flood the brain.

Fortunately, alcohol can give some warning signs as it penetrates into the brain and central nervous system so, if you spot the signs in yourself or a friend moderate your or their drinking, or stop drinking further amounts. The last thing you would want is to lose control, vomit or end up in hospital. Severe cases of heavy drinking can result in alcoholic poisoning, coma or death (link).

Your reactions also slow down, and as you drink more, you may become uncoordinated or unsteady on your feet. Your speech may get slurred and you may start seeing double. If you've had a lot to drink you may also experience strong emotional responses - for instance you may become aggressive or tearful. And because your judgement is impaired, you may do things that you might not normally do - from dancing on tables to going home with strangers. They may seem a good idea at the time, but can be extremely dangerous.