1. Chapter 6 The 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.  Flexion  Extension  Rotation  Abduction  Adduction  Circumduction Ordinary Body Movements - Skeletal

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  Nuclei are just beneath the sarcolemma  Sarcolemma – specialized plasma membrane  Sarcoplasmic reticulum – specialized smooth endoplasmic reticulum

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