Chapter 6 The Muscle Anatomy

1. Chapter 6The Muscle Anatomy

2. The Muscular System Functions • Movement • Maintain posture • Stabilize joints • Generate heat Three basic muscle types • Skeletal muscle* • Cardiac muscle • Smooth muscle

3. Muscles and Body Movements -Movement is attained due to a muscle moving an attached bone -Muscles are attached to at least two points • Origin – attachment to an immoveable bone • Insertion – attachment to a movable bone

4. Types of Muscles • Prime mover – muscle with the major responsibility for a certain movement • Antagonist – muscle that opposes or reverses a prime mover • Synergist – muscle that aids a prime mover in a movement and helps prevent rotation • Fixator – stabilizes the origin of a prime mover Hamstring Quads Calf & Glutes

5. Ordinary Body Movements - Skeletal • Flexion • Extension • Rotation • Abduction • Adduction • Circumduction

6. Special Movements - Skeletal • Dorsifelxion • Plantar flexion • Inversion • Eversion • Supination • Pronation • Opposition

7. Naming of Skeletal Muscles 1. Direction. Ex: rectus (straight) 2. Size. Ex: maximus (largest) 3. Location. Ex: many named for bones (temporalis) 4. Number of origins. Ex: triceps (three heads) 5. Origin & insertion. Ex: sterno (on the sternum) 6. Shape. Ex: deltoid (triangular) 7. Action. Ex: flexor & extensor (flexes or extends bone)

8. Characteristics of Muscles • Muscle cells are elongated (muscle cell = muscle fiber) • Contraction of muscles is due to the movement of microfilaments • All muscles share some terminology • Prefix myo refers to muscle • Prefix mys refers to muscle • Prefix sarco refers to flesh

9. Skeletal Muscle Characteristics • Most attached to bones by tendons • Multinucleate • Striated – visible banding • Voluntary – conscious control • Cells surrounded & bundled by connective tissue

10. Connective Tissue Wrappings • Endomysium – around single muscle fiber • Perimysium – around a fascicle (bundle) of fibers • Epimysium – covers the entire skeletal muscle • Fascia – on the outside of the epimysium

11. 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

12. Smooth Muscle Characteristics • No striations • Spindle-shaped cells • Single nucleus • Involuntary – no conscious control • Found mainly in the walls of hollow organs

13. Cardiac Muscle Characteristics • Has striations • Single nucleus • Joined to another muscle cell at an intercalated disc • Involuntary • Found only in the heart

14. Microscopic Anatomy of Skeletal Muscle • Sarcolemma – specialized plasma membrane • Sarcoplasmicreticulum – specialized smooth endoplasmic reticulum • Nuclei are just beneath the sarcolemma

15. Microscopic Anatomy of Skeletal Muscle Myofibrils - Bundles of myofilaments - aligned to give distrinct bands • I band = light band • A band = dark band Sarcomere - Contractile unit of a muscle fiber

16. Organization of the Sarcomere • Thick filaments = myosin filaments • protein myosin • ATPase enzymes • Thin filaments = actin filaments - protein actin

17. Microscopic Anatomy • Myosin filaments have heads (extensions or cross bridges) • Myosin and actin overlap somewhat • At rest, there is a bare zone that lacks actin filaments • Sarcoplasmic reticulum (SR) – for storage of calcium

18. Properties of Skeletal Muscle • Irritability – ability to receive and respond to a stimulus • Contractility – ability to shorten when an adequate stimulus is received

19. Nerve Stimulus to Muscles • Skeletal muscles must be stimulated by a nerve to contract • Motor unit - One neuron - Muscle cells stimulated by that neuron

20. Nerve Stimulus to Muscles • Neuromuscular junctions – association site of nerve and muscle