The Muscle SystemExam 3 ExtraSupplemental InstructionIowa State University

Leader: CodyCourse: AN S 214

Instructor: Dr. SelsbyDate:

1. Fill in the diagram at right and answer the pertaining questions:

2. What is the name of the neurotransmitter released at the NMJ?

3. What kinds of channels will this neurotransmitter open on the sarcolemma?

4. What major enzyme is present within the synaptic cleft? What is its function?

5. What is the significance of the junctional folds?

6. What kinds of receptors are located in the junctional folds?

7. What kinds of channels do they open?

8. What does this ion exchange initiate?

9. How do we repolarize the sarcolemma to get back to our original state?

10. Fill in the blanks and name structures A-D in the diagram below, illustrating the process of excitation-contraction coupling:

11. What kinds of channels are located at A? Describe the consequences of their activation.

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12. Draw the path of the end plate potential along the sarcolemma. What structure does it enter?

13. What is the effect of the spreading potential on the structure labeled C? D? Draw an arrow symbolizing any structural changes.

14. What particles are stored within the structure labeled B? What happens as a result of the conformational change to structure D?

15. What kinds of channels are located at B? Why do the intra-SR ions flood the cell?

16. What is the effect of these ions in the sarcoplasm?

17. What pump, by active transport, will pump calcium back into the SR?

18. What is the affect of Parvalbumin? Calsequestrin?

19. Number the following 1-6 in the order that they occur during a muscle contraction.ADP and Pi are expelled from the myosin head, allowing it to return to the relaxed 90º state.

1 The myosin head is in the relaxed state, at 90º. Bound to it is an ATP molecule.

Myosin heads bind to the now exposed binding sites on actin.

The flexion of a relaxing myosin head pulls its attached actin strand in towards the center of the sarcomere.

ATP on the myosin head is cleaved into ADP and Pi, forcing myosin heads into the high energy, 'cocked', position.

The myosin head binds an ATP molecule, allowing it to release actin.

20. How is acetylcholine moved away from receptors and the neuromuscular junction?

21. What happens if there is no longer an action potential? What happens to the electron dense feet?

22. What happens to the release of calcium?

23. What happens to troponin and tropomyosin?

24. Illustrate the actin-myosin interactions responsible for the observed tension potential in the blank boxes of the diagram to the right:

25. The amount of force generated by a muscle fiber is dependent on the degree of overlap between the actin and myosin subunits within the sarcomere. When there is ____________________ overlap, the _______________ strands become a physical obstruction to each other, and ________________ begins to butt into the Z-disks. When there is ___________________ overlap, too few myosin heads are able to form _____________________, decreasing the amount of force generated.

26. What are the 3 phases of a twitch and what event is correlated with each?

27. Label the diagram to the right’s axis and identify which line belongs to Type I and Type II fibers:

28. Which of these phases differ in length for fast and slow twitch muscle?

29. Why is contraction faster in fast twitch than in slow twitch muscle?

30. Why is relaxation faster in fast twitch than in slow twitch muscle?

31. Which type of muscle is primarily used for sustained levels of exercised? Short bursts of activity?

32. What type of muscle fiber would you expect to find in a 'natural sprinter'?A 'natural marathon runner'?

33. On the blank diagrams below, fill in the changes in tension that occur with multiple stimuli for both unfused and fused tetany. Use arrows to indicate stimuli and a line to track the change in muscle tension:

UNFUSED TETANY FUSED TETANY

34.How do these two types of tetany differ in frequency of stimulus?

35. How do these two types of tetany differ in amount of calcium released?

36. Which type of tetany can/cannot occur under normal physiological conditions?

37. Define threshold stimulus (illustrated in the figure to the right):

38. What accounts for the gradual increase in contractile strength?

39. What happens if the stimulus is below threshold?

40. What happens when the stimulus reaches maximal strength?

41. Name and define the two main types of muscle contractions discussed in class.

_____________________:

_____________________:

42. What are the two sub-types of isotonic contractions? Define each.

43. T/F: Muscles never push, they only pull.