#156--The human brain weighs about 1500 grams and "floats" on the cerebrospinal fluid inside the skull. This offers the brain some protection against sudden jolts or impacts. When dehydrated, there isn't enough of this fluid to displace the brain, and the brain literally sinks down. Impaired by its own weight, the brain loses neurons as they die due to a compromised blood supply. Additionally, the brain is 85% water. So like a plum slowly turning into a prune, chronic dehydration causes the brain to shrink and key regulatory functions to be inhibited. So if you're smart, you'll drink enough pure, clean water to stay that way.