Final answer:
The muscle that stabilizes the origin of another muscle is known as a fixator. It is a specific type of synergist that helps the prime mover, or agonist, to perform movements more effectively.
Step-by-step explanation:
The muscle that stabilizes the origin of another muscle is called a fixator. The muscle primarily responsible for a movement is known as the prime mover, or agonist, and muscles that assist in this action are called synergists. A special type of synergist that specifically stabilizes the origin of the agonist to allow for more efficient movement is known as a fixator. On the contrary, a muscle with the opposite action of the prime mover is known as an antagonist. Antagonists help maintain body or limb position and control rapid movements. Synergists can also assist agonists, but a fixator is distinct because it provides stability to the bone where the prime mover's origin is attached.