This fact seems to have originated from claims made by plastic surgeon Anthony Youn MD, writing at CNN and widely reported elsewhere. The catch is that it only applies to people undergoing a breast lift or reduction, who smoke in the month before and after surgery. So most smokers can relax (about the nipple thing, at least).
So go to bed, or your brain might get too big for your skull and make your head explode. Or not – turns out this factoid comes from a study done on fruit flies. And it's the synapse size/number that increases during a fly's waking hours, not its actual brain.
No they are not.
We've covered it before, but this myth never seems to die. It might have originated from the fact that 10% of the brain is made up of neurons, and the remaining 90% is glial cells. We don't really know what glial cells do, but that doesn't mean we don't use them.