1. A prime mover, or , produces a particular type of movement. a. agonist c. fixator b. antagonist d. synergist 2. Circle True or False. Muscles of facial expression differ from most skeletal muscles because they usually do not insert into a bone. 3. Muscles that act on the cause movement at the hip, knee, and foot joints. a. lower limb b. trunk c. upper limb 4. This two-headed muscle bulges when the forearm is flexed. It is the most familiar muscle of the anterior humerus. It is the: a. biceps brachii c. extensor digitorum b. flexor carpii radialis d. triceps brachii 5. These abdominal muscles are responsible for giving me my "sixpack." They also stabilize my pelvis when walking. They are the muscles. a. internal intercostals c. quadriceps b. rectus abdominis d. triceps femoris.