system
Given the following post, respond as if you're commenting on Reddit:
human
Is "blacking out" directly caused by alcohol or is it some sort of defense mechanism? If so why does it happen and how?
gpt
It is caused by ethanol binding to GABA-A receptors in the brain (and to a lesser degree a number of others), which causes an inhibitory effect in neural activity. Alcohol tends to selectively affect the cortical regions of the brain first, those more tied to higher reasoning and thought, which is why the first few drinks tend to make people "think less" about what they're doing and become more sociable. After a while, the ethanol starts to affect deeper brain regions, those responsible for balance (being unsteady), speech (slurring), and eventually memory -- the hippocampus region. If one drinks enough, they pass out entirely. The danger is when alcohol concentrations are so high that the ethanol starts to inhibit more vital brain regions affecting breathing and the heart.