U nit 1: Muscles

1. Unit 1:Muscles Week 1 Click images for hyperlinks!

2. What is a muscle? • Muscles are organs made of muscular and connective tissues, which make up the Muscular System • They attach to bones and other muscles so that when they contract, they produce motion • There are three different types of muscle: • Skeletal • Cardiac • Smooth

3. Muscle Tissue • Muscle tissue: Collection of muscle cells which contain sarcomeres • Sarcomere: a single contractile unit made of primarily actin, myosin, and titin

4. Sarcomere • M-line • Only myosin • Doesn’t move • Z-disk • Perimeter of sarcomere • Moves toward M-line with contraction • I-band • Actin + titin • Spans width of titin • Shrinks with contraction • A-band • Actin + myosin • Spans width of myosin • H-zone • Only myosin • Gets smaller with contraction Myosin Actin

5. Sarcomere Proteins • Actin • G-actin: Globular individual pearl-like actin molecules • F-actin: G-actin pearls assemble into a Filament of actin • Myosin pulls actin inward • Contains head and tail units • Myosin head binds to actin, pulls it inward to contract • Titin pushes z-discs outward • Elastic, holds myosin in place and helps re-extend sarcomere upon relaxation

6. Video- Sarcomere Contraction Click video to watch

7. Arrangement of Fibers • Many sarcomeres together make up a myofibril • Many myofibrils make up a muscle fiber (cell) • Coated by endomysium • Many fibers make up a fiber bundle • Coated by perimysium • Many bundles make up the entire muscle • Coated by epimysium

8. Types of Muscle • Smooth *Found in organs (GI, vessels) for constriction -Involuntary -Non-striated -Mononucleate -Parallel fibers • Cardiac *Only in the heart for moving blood -Involuntary -Striated -Mononucleate -Branched Fibers -Intercalated Discs • Skeletal *Connected to muscle for voluntary motion -Voluntary -Striated -Multinucleate -Parallel fibers

9. Types of Muscle

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