Now, one of these muscles is known as an agonist, the other muscle is known as an antagonist. And these roles basically change with respect to the type of motion that we are actually creating. And we'll see what that means in just a moment. So the biceps triceps system works together in an autogenous manner. So the triceps biceps system is controlled antagonistically. And what that basically means is when one of these muscles contracts, the other muscle actually stretches, it elongates and vice versa.