The Muscle System
Exam 3 Extra
Supplemental Instruction
Iowa State University
1. Fill in the diagram at right and answer the
pertaining questions:
Leader: Cody
Course: AN S 214
Instructor: Dr. Selsby
Date:
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:
Supplemental Instruction
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11. What kinds of channels are located at A? Describe the consequences of their activation.
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?
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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. Ho
w 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.
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43. T/F: Muscles never push, they only pull.