Ch 36 Musculoskeletal System AP lecture

Three vertebrate muscles Skeletal – A.k.a striated – Voluntary movements

Cardiac – Involuntary – Beating of the heart – Appears striated because of myosin and actin – Smaller than skeletal – Cells attached by gap junctions

Smooth – Involuntary – Movement of internal organs – Internal organs controlled by ANS – Smaller than skeletal – Do not appear striated because of the actin and myosin arrangements

Muscle contraction Skeletal muscle cells and muscle fibers are bundled together by connective tissue Interactions between actin and myosin – Every muscle fiber is made of myofibrils- actin and myosin in repeating segments called sarcomeres

Muscle voluntary, striated involuntary, striated auto-rhythmic involuntary, non-striated evolved first multi-nucleated digestive system arteries, veins heart moves bone

Actin Thin filaments Long chains of actin monomers twisted around each other. Twisted around that chain is tropomyosin and attached to that is troponin. – These control contractions and relaxation

Myosin Two long polypeptide chains coiled together. Each ends in a large globular head. Myosin filaments have many myosin molecules

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ATP feeds the contractions Immediate system uses ATP Glycolytic system metabolizes carbohydrates to lactate and pyruvate Oxidative system metabolizes carbohydrates or fats into water and carbon dioxide

Where is ATP needed? Cleaving ATP  ADP allows myosin head to bind to actin filament thin filament (actin) thick filament (myosin) ATP myosin head form cross bridge binding site ADP release cross bridge shorten sarcomere 1

Put it all together… 1 ATP

Vertebrate skeleton 206 bones Axial skeleton – Skull, vertebral column,sternum and ribs Appendicular skeleton – Pectoral girdle, pelvic girdle, arm, leg, hands and feet bones

Important bones

Bone growth

Joints Two bones join and muscles work in antagonistic pairs – Flexor – Extensor Types of joints – Ball and socket – Pivot – Hinge

Tendon Ligament