Once alcohol gets past the liver and into the general circulation the brain is one of the first organs to be affected.
Basically alcohol acts as a sedative, but some parts of the brain seem more susceptible than others and this explains the characteristic changes seen in drinkers.
The first part of the brain to be affected is the frontal lobe - the part that controls our social behaviour and suppresses our more primitive instincts.
Shutting down our frontal lobes disinhibits us and explains why we become more outgoing after a few drinks - so called "Dutch courage".
As the alcohol levels rise, so other parts of the brain are affected - particularly the centres responsible for speech, vision, posture and movement - with knock on effects like slurring of words, elbow slipping off the table and difficulty reading the back of your party CD.
Judgement is also seriously impaired and this, combined with the disinhibition, is why driving, after even small amounts of alcohol, is dangerous.
As levels rise further, more basic functions are affected and very high levels can render the drinker unconscious and even interfere with the control of breathing.
A serious overdose of alcohol can be, and often is, fatal.
Prolonged heavy drinking over many years can lead to significant brain damage and loss of intellectual capability.