Which facial muscle action is primarily responsible for frowning by pulling the eyebrows inferiorly and medially?

In the context of muscle actions, what best describes a prime mover (agonist) muscle?

Which muscle group is primarily responsible for extending the knee joint?

In muscle actions, which term describes a muscle that opposes or reverses a movement produced by another muscle?

Which muscle is the primary extensor of the thigh at the hip joint?

Which muscle is the primary extensor of the elbow joint?

Which muscle elevates the eyebrows?

In muscle actions, which term describes a muscle that opposes or reverses the movement produced by the prime mover (agonist)?