1. Chapter 8: Muscular System
Section 1: Anatomy

4. The Muscular System Functions:
Muscles are responsible for all types of body movement
Functions:
Producing movement
Maintaining posture
Stabilizing joints
Generating Heat

5. Characteristics of muscles
Muscle cells are elongated
muscle cell = muscle fiber
Contraction of muscles is due to the movement of microfilaments

6. Terminology of Muscles
All muscles share some terminology
Prefix myo refers to muscle
Prefix mys refers to muscle
Prefix sarco refers to flesh

7. Three basic muscle types are found in the body
3 types of muscles
Three basic muscle types are found in the body
Skeletal muscle
Cardiac muscle
Smooth muscle

8. 1. Skeletal Muscle Characteristics
Most are attached by tendons to bones
Cells are multinucleate
Striated – have visible banding
Voluntary – subject to conscious control
Cells are surrounded & bundled by connective tissue

9. 2. Smooth Muscle Characteristics
Has no striations
Spindle-shaped cells
Single nucleus
Involuntary – no conscious control
Found mainly in the walls of hollow organs
Figure 6.2a

10. 3. Cardiac Muscle Characteristics
Has striations
Usually has a single nucleus
Joined to another muscle cell at an intercalated disc
Involuntary
Found only in the heart
Figure 6.2b

11. Let’s look at skeletal muscles more closely….

12. Connective Tissue Wrappings of Skeletal Muscle
Endomysium – around single muscle fiber
Perimysium – around a fascicle (bundle) of fibers
Figure 6.1

13. Connective Tissue Wrappings of Skeletal Muscle
Epimysium – covers the entire skeletal muscle
Fascia – on the outside of the epimysium
Figure 6.1

14. Skeletal Muscle Attachments
Epimysium blends into a connective tissue attachment
Tendon – cord-like structure
Aponeuroses – sheet-like structure
Sites of muscle attachment
Bones
Cartilages
Connective tissue coverings

15. Microscopic Anatomy of Skeletal Muscle
Cells are multinucleate Reminder*
Cell or fiber (same thing)
Figure 6.3a

16. Microscopic Anatomy of Skeletal Muscle
Sarcolemma
specialized plasma membrane
Nuclei are just beneath the sarcolemma
Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum for storage of calcium
Figure 6.3a

17. Microscopic Anatomy of Skeletal Muscle
Myofibril
Bundles of myofilaments
Myofibrils are aligned to give distinct light and dark bands
I band = light band
A band = dark band
Figure 6.3b

18. Microscopic Anatomy of Skeletal Muscle
Sarcomere
Contractile unit of a muscle fiber
Has thin and thick filaments
Figure 6.3b

19. Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thick filaments = myosin filaments **From Z line (disc)
Composed of the protein myosin to Z line (disc)
Has ATPase enzymes
Figure 6.3c

20. Microscopic Anatomy of Skeletal Muscle
Organization of the sarcomere
Thin filaments = actin filaments
Composed of the protein actin
Figure 6.3c

21. Microscopic Anatomy of Skeletal Muscle
Myosin filaments (thick filaments) have “heads” (-extensions, or cross bridges)
Myosin and actin Thin &
thick filaments
overlap somewhat
Figure 6.3d

22. Microscopic Anatomy of Skeletal Muscle
At rest, there is a bare zone that lacks actin filaments
Figure 6.3d

23. Thick Filament (myosin)
Fascicle
Muscle (organ)
Muscle Fiber (cell)
Myofibril
Muscle Fiber
(with many nuclei)
Sarcomere
Thin Filament (actin)
Thick Filament (myosin)

24. Be prepared for some dissections!!!!