Alcohol affects various centers in the brain, both higher and lower order. The centers are not equally affected by the same BAC -- the higher-order centers are more sensitive than the lower-order centers. As the BAC increases, more and more centers of the brain are affected.
The order in which alcohol affects the various brain centers is as follows:
1. Cerebral cortex
2. Limbic system
4. Hypothalamus and pituitary gland
5. Medulla (brain stem)
Source - http://health.howstuffworks.com/well...l/alcohol6.htm