Today's lecture is about a chemical you may regret you used, probably in the weekend -- I'm talking of course about alcohol. Well, many of you are very familiar about how to use it but how much do you know about it? Well, alcohol is a depressant, meaning it slows down the activity of your central nervous system by replacing the water around the nerve cells in your body. When you drink an alcoholic beverage, your body absorbs about 90% of the alcohol in the drink. On average, a normal liver can process 10 grams of alcohol per hour. That is the equivalent of a glass of wine. Alcohol also changes the density of the fluid and tissues in the part of your ears that control your sense of balance. That's why it can be difficult to walk, or even stand up, when you've had too much to drink. Why do we feel bad in the morning? Now we have to get a little technical. Your liver processes alcohol into a toxic chemical called acetaldehyde. Just as the alcohol made you feel good, or at least drunk, the acetaldehyde makes you feel bad. It causes your blood vessels to dilate -- which makes you feel warm, and gives you a headache. Meanwhile, the alcohol still in your system is raising both your pulse and blood pressure -- which makes the headache even worse. And then there's the effect on your kidneys. When you're sober, your kidneys use a chemical called vasopressin to recycle the water in your body. But alcohol reduces the level of vasopressin in your blood. So, instead of recycling water, you urinate it out. That makes you dehydrate which can make you feel worse, what we call a hangover. So, if you really want to reduce some of the effects of a hangover you can drink a lot of water before you go to bed.