The checks and balances system in the USA Constitution

Source: http://www.socialstudieshelp.com/lesson_13_notes.htm

Here you have some additional information to learn more about the system of checks and balances designed in the USA Constitution to prevent abuse of power. This short video explains how every branch of power controls the other ones and how there is also a balance between the power of the Federal Government and the power of the States: 

And this is a more extended document: 

http://americanhistory.about.com/od/usconstitution/a/checks_balances.htm