The Muscle System



The Muscle System

Muscle Cells and Muscle Contraction Web Activity

In this activity you will explore both the structure (anatomy) and function (physiology) of skeletal muscle. Skeletal muscles work by pulling on bones. In order to pull on the bones the muscle length must shorten. This is a characteristic of muscle tissue known as contractility. The proposed mechanism for this contraction is called the sliding filament theory. Muscle cells (aka myofibers or muscle fibers) are made up of bundles of filaments called myofibrils. The filaments contained within these fibrils are made of protein. There are 2 main protein filaments you need to know. Actin is the protein that composes the thin filaments while myosin is the protein that composes the thick filaments. Additional proteins found in the myofibrils include tropomyosin, troponin and titin.



When the page opens, there will be a short introduction with the objectives of the animation. Move to the next slide by clicking the arrow on the lower right corner. Use the information in the animation to answer these questions on a separate sheet of paper.

1. What are myofibrils and how big are they?

2. Where are the sarcomeres located?

3. What is the sarcolemma?

1. What are transverse tubules-tubules?

4. How are the nerve impulses for contraction transmitted?

5. Where in the myofiber are mitochondria and nuclei located?

6. Drag the labels to the correct spot on the diagram – you have to complete this before you move on.

7. What are the bands that mark the sarcomere’s borders know as?

8. What are the lightest and least dense structures of a sarcomere?

9. What are the 3 proteins found in thin filaments?

10. Drag the labels to the correct part of the sarcomere – you must complete this to move on.

11. Draw a relaxed sarcomere

12. Draw a contracted sarcomere

13. Describe what happens to the H-zone and the I-band during contraction.

14. What happens in the sliding filament theory of contraction (copy it from the right column).

15. What is a cross bridge?

16. What causes the contraction of a sarcomere?

17. Why do the thin filaments not completely overlap the thick filaments?

18. What must the sarcomere do to relax?

19. What is titin and what does it do?

20. What drives a muscle contraction?

21. Where within the myofiber are calcium ions stored?

22. What stimulates the release of calcium?

23. To what does the calcium ion bind?

24. What happens to ADP during a “power stroke”?

25. What causes the release of myosin from the actin?

26. List the events of muscle contraction in order – you must complete this step to move on – copy the steps on your paper.

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