1. Bellringer 12/9 Label #4 and #5

2. Building Skeletal Muscle… We will identify the different structures within a skeletal muscle by building a model.

3. Procedure: Wrap each of 27 pipe cleaners in a thin piece of Saran wrap. What does each pipe cleaner represent? What does the Saran wrap represent?

4. Procedure: Join 3 wrapped pipe cleaners together-this will form a fascicle. Wrap the sets of three in another sheet of Saran wrap. What does the Saran wrap represent?

5. Procedure: Join together the 9 fascicles that you created-use two rubber bands and cover the outside with Saran wrap. What does the Saran Wrap represent this time? This creates a skeletal muscle

6. Label the following on the first page of your handout… Muscle fiber, epimycium, perimysium, endomysium, fascicle Color the picture and create a key. Use a different color for each structure.

7. Build a sarcomere… The theory that describes the way that skeletal muscles contract is called the Sliding Filament Theory. Cut out your pieces to the sliding filament model. Use 2 different colors of paper. Assemble them as explained on the paper and staple both ends. Label as shown in the diagram

9. Label the second page of your handout… The pictures show:  An electron micrograph of a sarcomere  A drawing of a relaxed sarcomere  A drawing of a contracted sarcomere  Label the following in all three drawings: z discs, H zone, I band, A band, M line, actin, myosin, sarcomere  (don’t label actin, myosin or H zone in the electron micrograph)  Color all three drawings and create a key. Use the same colors for the structures in all three drawings.

10. How does a sarcomere work???  A sarcomere is the smallest unit of skeletal muscle that can contract  Sarcomeres repeat themselves over and over along the length of the myofibril

11. Steps for muscle contraction: 1.) a nervous impulse arrives at the neuromuscular junction, which causes a release of the neurotransmitter, acetylcholine The presence of acetylcholine causes Calcium to be released from the Sarcoplasmic reticulum

12. Steps for muscle contraction 2.) The presence of calcium facilitates the formation of a cross-bridge, allowing the myosin filaments to attach to the actin 3.) Energy from ATP enables the myosin to pull the Actin filaments inward, shortening the muscle. This occurs along the entire length of every myofibril in the muscle cell.

13. Steps for muscle contraction 4.) An ATP molecule binds to the Myosin head and allows the Myosin to detach from the Actin. When the ATP is broken down, the Myosin can again attach to the Actin and the “power stroke” can be repeated. The muscle contraction can last as long as there is adequate calcium and ATP. Once the impulse stops, the calcium is pumped back into the sarcoplasmic reticulum and the actin returns to its resting position allowing the muscle to lengthen and relax.