Why do we raise our hands towards the sky?

I attend a first baptist church and not often do people respond with amen or anything of that nature but when they do, they really do. However, I was just wondering why, when people get excited, that they raise their hands to the ceiling? At another church I attended, a preacher said that we needed to know what we were doing when we raised our hands because to some people it meant we were praising God. What does it really mean? Serious answers only.