1. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Attachments  Epimysium blends into a connective tissue attachment at the ends of muscles 2 Types 1.Aponeuroses—sheet-like structures of connective tissue (sometimes referred to as fascia)  Attach muscles to bones, cartilages, or connective tissue coverings  can be stretched by muscular contraction, absorbing energy like a spring and returning it when they recoil to unloaded conditions

2. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Skeletal Muscle Attachments 2.Tendons—cord-like structures  Mostly collagen fibers  Often cross a joint due to toughness and small size

3. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of a Muscle Fiber  Sarcolemma—specialized plasma membrane  Sarcoplasm- cytoplasm of muscle cells; contains large amounts of stored glycogen and an oxygen-binding protein, myoglobin  Sarcoplasmic reticulum— specialized smooth endoplasmic reticulum Stores and releases calcium Surrounds the myofibril

4. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of a Muscle Fiber  Myofibrils- long organelles inside muscle cell extending the entire length of the cell; hundreds to thousands in each fiber/cell (80% of cell volume)

5. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Myofibril  Sarcomere— repeating unit along the myofibril contractile unit of a muscle fiber made of myofilaments

6. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Sarcomere  Myofilaments  2 Types in a sarcomere 1.Actin filaments Thin filaments  Composed of the protein actin  Anchored to the Z disc (which is a membrane)

7. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Sarcomere 2. Myosin filaments Thick filaments =  Composed of the protein myosin  Has ATPase  Myosin filaments have heads (extensions, or cross bridges)  Myosin and actin overlap somewhat

8. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Myofilament Figure 6.3c

9. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle  Myofilaments are aligned to give distinct bands  I band = light band  Contains only actin (thin) filaments  A band = dark band  Contains the entire length of the mysosin (thick) filaments

10. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings

11. Microscopic Anatomy of the Sarcomere striations - repeating series of dark and light bands A bands- dark bands -H zone- lighter stripe in midsection of an A band; visible when muscle is relaxed -M line- dark line bisecting each H zone I bands- light bands - Z line- dark line bisecting each I band

12. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of Skeletal Muscle Figure 6.3b