11.9: Applied Thinking Self‑Check

Word bank (use as needed)

fascicle, parallel, fusiform, convergent, unipennate, bipennate, multipennate, circular, origin, insertion, agonist, antagonist, synergist, fixator, lever, fulcrum, moment arm, torque, naming (location, shape, size, fiber direction, heads, attachments, action), axial, appendicular, suprahyoid, infrahyoid, sternocleidomastoid, facial nerve (CN VII), aponeurosis, linea alba, diaphragm, pelvic floor, rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis), scapulohumeral rhythm, hamstrings, quadriceps, patella.

Questions

1. What effect does fascicle arrangement have on a muscle’s action?
   • Include: force vs range/speed trade‑off (pennate = more force; parallel/fusiform = more range/speed) and one example (e.g., deltoid vs sartorius).
2. Movements of the body occur at joints. Describe how muscles are arranged around joints.
   • Include: agonist–antagonist pairs, synergists, fixators; how crossing a joint and line of pull determine action.
3. Explain how a synergist assists an agonist by being a fixator.
   • Include: stabilizing origin/nearby bone to improve the prime mover’s line of pull; example (scapular stabilizers helping biceps curl)
4. Why are the muscles of the face different from typical skeletal muscle?
   • Include: many insert into skin (not bone) to move skin for expression; innervation by facial nerve (CN VII); example (orbicularis oris closes lips).
5. What are some similarities and differences between the diaphragm and the pelvic diaphragm?
   • Include: both form muscular floors; diaphragm = breathing (inspiration), pelvic diaphragm = organ support/continence; different actions/innervation and clinical roles.
6. The tendons of which muscles form the rotator cuff? Why is the rotator cuff important?
   • Include: SITS (supraspinatus, infraspinatus, teres minor, subscapularis); cuff compresses/stabilizes the humeral head and guides rotation; common injury risk.
7. Which muscles form the hamstrings? How do they function together?
   • Include: biceps femoris (long head), semitendinosus, semimembranosus; hip extension + knee flexion; role in gait and deceleration.
8. Which muscles form the quadriceps? How do they function together?
   • Include: rectus femoris, vastus lateralis, vastus medialis, vastus intermedius; knee extension (rectus also flexes hip); patella improves moment arm.
9. How does lever class and moment arm affect muscle performance at a joint?
   • Include: bones as levers, joint as fulcrum, tendon as effort; third‑class levers favor speed/range, second‑class favor force; example (biceps curl vs heel raise).