Muscular System

Criteria for Naming Muscles

1. Direction of muscle fibers
   1. rectus = parallel to midline
      1. rectus abdominus
   2. transverse
   3. oblique
2. Location over bone, muscle, origin, or insertion
   1. example: sternocleidomastoid
3. Size
   1. maximus
   2. medius
   3. minimus
   4. longus
   5. brevis
   6. example: gluteus maximus
4. Distinctive Shape
   1. example: deltoid
5. Action of muscle at joint
   1. example: supinator
6. Number of origins
   1. bi- , tri-, quad-
   2. examples: biceps, quadriceps

Definitions

1. Primer mover or agonist
   1. muscle primarily responsible for the action
2. Antagonist
   1. opposes agonist movement
   2. may help to prevent tension overload
   3. force dampening
3. Synergist
   1. aids "agonist"
   2. may be a fixator which stabilizes bone to allow for movement (especially in the shoulder girdle)

Selected prime movers for specific body movements

1. Mastication (Chewing)
   1. Masseter
2. Biting
   1. Masseter, temporalis
3. Smiling
   1. Zygomaticus
4. Nodding
   1. Sternocleidomastoid
   2. Origin- sternum,clavicle; Insertion- mastoid/temporal
5. Kissing
   1. Orbicularis oris
6. Blinking
   1. Orbicularis oculi
7. Trunk Flexion - (Abdominal wall)
   1. External obliques (outer)- medial, down
   2. Internal oblique - medial, up
   3. Transverse abdominus
      1. tendon of all 3 inserts on linea alba
   4. Rectus abdominus
      1. publis to ribs along linea alba- tendon inscriptions
8. Respiration
   1. Diaphragm,External intercostals - active in inspiration
9. Shoulder abduction
   1. Deltoid (also involved in shoulder flexion,extension)
10. Shoulder adduction
    1. Pectoralis Major
    2. Latissimus Dorsi
       1. Lats & Pecs only shoulder muscles originating on axial skeleton (spine, sternum, respectively)
11. Shoulder flexion
    1. Deltoid
    2. Pectoralis Major
12. Shoulder Extension
    1. Deltoid
    2. Latissimus Dorsi
13. Other muscles acting on scapula
    1. Trapezius
       1. elevates,depress, adduct scapula
    2. Rhomboids
       1. adduct scapula
    3. Serratus anterior
       1. abducts scapula
    4. Rotator cuff (originate on scapula but move the humerus)
       1. Supraspinatus
       2. Infraspinatus
       3. Subscapularis
       4. Teres minor
14. Elbow flexion
    1. Biceps brachii
    2. Brachialis (stronger)
15. Elbow Extension
    1. Triceps brachii
       1. long head originates on scapula
    2. Anconeus (assistor)
16. Hip flexion
    1. iliopsoas
       1. Psoas major & iliacus (common insertion-femur)
       2. psoas major (O= lumbar spine) used in straight leg sit- ups rather than abdominus
       3. when legs fixated, flex trunk (Bending)
17. Hip extension (Posterior Muscles of thigh)
    1. Biceps Femoris
       1. part of the hamstirngs along with semitendinosus, semimembranosus
       2. also Prime mover for knee Flexion
    2. Gluteus Maximus
18. Knee extension
    1. Quadriceps femoris:
       1. Rectus Femoris
       2. "Vastus" group
          1. vastus lateralis
          2. vastus medialis
          3. vastus intermedius
       3. very powerful group
       4. normally hamstrings only 2/3 as strong
19. Knee flexion
    1. Biceps femoris, semimembranosus, semitendinosus
       1. Posterior compartment
          1. Flexes knee, extends thigh
20. Thigh Abduction
    1. Lateral muscles of thigh
       1. Tensor fasciae latae - inserts on iliotibial tract stabilizes knee, flexes,abducts thigh
    2. Gluteus medium, minimus
    3. Piriformis
21. Thigh Adduction
    1. Medial muscles of thigh (adductors)
    2. Act only on the femur
    3. Adductor magnus, longus, brevis
    4. Gracilis
       1. also adducts thigh and assists in flexion
    5. Pectineus
22. Dorsiflexion of ankle
    1. Anterior compartment
       1. Tibialis Anterior
       2. also extensors(digitorum longus,hallucis)
23. Plantar flexion of Ankle
    1. Posterior compartment
       1. Gastrocnemius
          1. gastroc - 2 jointed muscle (Origin= femur Insertion= calcaneus)
       2. Soleus
          1. deep to gastroc
    2. Most powerful movement of ankle,foot
       1. push off, tip toes
    3. Other muscles in posterior compartment:
       1. plantaris
       2. popliteus
       3. tibialis posterior
       4. flexor digitorum longus
       5. flexor hallucis longus
24. Movements in wrist & fingers
    1. Posterior compartment
       1. extension
       2. supination
    2. Anterior compartment muscles
       1. flexion
       2. pronation
          1. examples: flexor digitorum or flexor carpi
             • 2 jointed muscles (Origin= humerus Insertion= metacarpal,phlanges)