1. Chapter 9: Muscular System

2. Types and Functions of Muscles
Skeletal muscle
Generally attached to bone and controlled by choice
Cells are long/appear striped (striated)
Smooth muscle
Generally found in the walls of viscera
Functions automatically
Cardiac muscle
Found only in heart
Cells are long and branching

3. Types and Functions of Muscles (cont’d.)
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4. Copyright © 2007 by Saunders, an imprint of Elsevier Inc.
Muscle Structure
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5. Whole Muscle Structure
Belly: fleshy body of muscle between slender points of attachment
Fascia: layers of tough connective tissue surrounding large skeletal muscles
Epimysium: outermost layer of fascia
Perimysium: surrounds small bundles of fibers (middle)
Endomysium: surrounds individual muscle fibers (inner)
Tendon: strong, cordlike fascia that extends toward and attaches to bone

6. Muscle Fiber Structure (Muscle cell)
Sarcolemma: cell membrane of a muscle fiber
Transverse tubules: points of cell membrane that penetrate deep into interior of muscle fiber
Sarcoplasmic reticulum: specialized endoplasmic reticulum within muscle fiber
Myofibrils: long cylindrical structures in each muscle fiber
Sarcomeres: contractile units formed of proteins actin and myosin

7. Sliding Filament Theory
Muscles contract because sarcomeres shorten
Sarcomeres shorten because actin and myosin filaments slide past each other
Myosin heads make contact with actin when stimulated
Myosin heads rotate, pulling actin toward the center of the sarcomere and causing the actin to slide past myosin

8. Role of Calcium and ATP Contraction and relaxation of muscle:
ATP allows the actin and myosin to interact in the presence of calcium
Calcium: stored in sarcoplasmic reticulum, away from actin and myosin
Muscle relaxation: calcium is stored in SR
Muscle contraction: calcium is released from SR
Muscle relaxation: calcium is pumped back into SR

9. Skeletal Muscles and Nerves
Motor nerve: type of nerve that supplies skeletal muscle with stimulation
Neuromuscular junction (NMJ): area where motor nerve meets muscle fibers

10. Muscle Contraction
The electrical signal (nerve impulse) travels down the nerve to the terminal and causes the release of the neurotransmitter Ach (acetylcholine).
The ACh diffuses across the neuromuscular junction and binds to the receptor sites.
Stimulation of the receptor sites causes an electrical impulse to form in the muscle membrane. The electrical impulse travels along the muscle membrane and penetrates deep into the muscle through the T-tubular system

11. Muscle Contraction (cont’d.)
4. The electrical impulse stimulates the sarcoplasmic reticulum to release calcium into the sarcomere area.
The calcium allows the actin, myosin, and ATP to interact, causing muscle contraction. This process continues as long as calcium is available to the actin and myosin.
Muscle relaxation occurs when calcium is pumped back into the sarcoplasmic reticulum, away from the actin and myosin.

12. How Skeletal Muscles Are Named
Characteristics of skeletal muscles:
Size (ex: vastus= huge)
Shape (ex: deltoid=triangular)
Direction of fibers (transverse=across)
Location (ex: pectoralis= chest)
Number of origins (ex: biceps= 2)
Identification of origin and insertion (ex: sternocleidomastoid)
Muscle action (ex: flexor muscle=causes flexion)
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13. Muscles from Head to Toe
Anterior view
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14. Muscles from Head to Toe (cont’d.)
Posterior view
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15. Muscles of the Head & Neck
Facial muscles
Frontalis
Orbicularis oculi
Orbicularis oris
Buccinator
Zygomaticus
Chewing muscles
Temporalis
Masseter
Neck Muscles
Sternocleidomastoid
Trapezius

16. Muscles of the Trunk Muscles involved in breathing Intercostal muscles
Diaphragm

17. Muscles of the Abdominal wall
External oblique
Internal oblique
Transversus abdominis
Rectus abdominis

18. Muscles That Move the Shoulder and Upper Arm
Trapezius
Serratus anterior
Pectoralis major
Latissimus dorsi
Deltoid
Rotator cuff muscles

19. Muscles That Move the Forearm and Hand
Biceps brachii
Triceps brachii
Brachialis
Brachioradialis

20. Muscles We Sit On
Gluteus maximus
Gluteus medius
Gluteus minimus

21. Muscles That Move the Leg
Quadriceps femoris (anterior thigh)
Rectus femoris
Vastus lateralis
Vastus medialis
Vastus intermedius
Sartorius (Across thigh)

22. Muscles That Move the Leg
Hamstrings (posterior thigh)
Biceps femoris
Semitendinosus
Semimembranosus

23. Muscles That Move the Ankle and Foot
Tibialis anterior
Peroneus longus
Gastrocnemius
Soleus