Natalia,
In a standard setup, scrolling is not an interaction that counts towards calculating the bounce rate. No matter how much a visitor scrolls your page up and down it is still recorded as a bounce if the visitor doesn't go to another page (...or, and here is the think we can use to our advantage, generate an event).
If you have a one-page website you will see a very high bounce rate no matter how much time each visitor spends reading it, or scrolling up and down. What you can do to get the bounce rate to make more sense, is to fire an event - either after x seconds, or when a visitor has scrolled the page. Found this blog page that gives more details about this:
http://drawingablank.me/blog/fix-your-bounce-rate.htmlGood luck,
//J