Anatomy and Physiology / Unit 5: The Muscular System
5.6 Major Muscles and Movement
Notes
Muscles produce movement by pulling on bones across joints. The origin is the less movable attachment; the insertion is the more movable one. The prime mover (agonist) produces the movement, the antagonist opposes it, synergists assist, and fixators stabilize.
- Movements: flexion (decreases angle), extension (increases angle), abduction (away from midline), adduction (toward midline), rotation, circumduction, dorsiflexion and plantar flexion (ankle), supination and pronation (forearm).
- Major muscles: deltoid (abducts arm), pectoralis major (flexes and adducts arm), latissimus dorsi (extends and adducts arm), biceps brachii (flexes elbow), triceps brachii (extends elbow), rectus abdominis (flexes trunk), quadriceps femoris (extends knee), hamstrings (flex knee), gluteus maximus (extends hip), gastrocnemius (plantar flexion), tibialis anterior (dorsiflexion), trapezius (elevates scapula), diaphragm (breathing).
- Example: in bending the elbow the biceps is the agonist and the triceps is the antagonist.
Practice
When you straighten your knee to kick a ball, which muscle group is the prime mover?
The quadriceps extend the knee. Hamstrings are the antagonists.
Raising the arm out to the side away from the body is called:
Abduction moves a limb away from the midline; the deltoid is a main mover.
During a biceps curl, the triceps brachii acts as the:
The triceps opposes elbow flexion, so it is the antagonist.
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