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PhysioEx 9.0 EXERCISE 2 ACTIVITY 1 - 7.
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This is a big help.  I think I understand the labs sometimes and then it turns out that I don't.  Sad

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Activity 1- The Muscle Twitch and the Latent Period
1.   Define the terms skeletal muscle fiber, skeletal muscle twitch, electrical stimulus, and latent period.
A skeletal muscle fiber is a single skeletal muscle cell (or myocyte). These cells are multinucleated and contain many myofibrils arranged in a cylindrical structure. The myofibrils themselves are composed of repeated sarcomeres containing actin and myosin proteins, which serve as the functional unit of a muscle. Muscles are composed of many individual muscle fibers. A skeletal muscle twitch is defined as the mechanical (contractile) response of a muscle to a single action potential. An action potential can be generated in a muscle cell if the motor neuron sends a stimulus that produces a large enough graded depolarization of the end-plate potential. An electrical stimulus is an electrical impulse that directly stimulates muscle cells via an electrode. This stimulation mimics the action potential of a motor neuron and subsequent acetylcholine release at neuromuscular junctions, ultimately to generate muscle contraction. The latent period is the period of time that elapses between the generation of an action potential and the beginning of the contraction phase in a muscle cell. While no force is generated during this period, chemical changes occur within the myocyte in preparation for contraction. For example, calcium ions are released from the sarcoplasmic reticulum into the sarcolemma.



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thank you so much!



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I don't currently have anything meaningful to "add" to the thread, but I am sure that this forum will be very helpful!  I hope to help others when possible.



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ACTIVITY 7:  Isotonic Contractions and the Load-Velocity Relationship

41. The fastest muscle contraction velocity measured in this part of the simulation occurred with the ______ weight.
a. 2.0 gm
b. 1.5 gm         
c. 1.0 gm
d. 0.5 gm

42. The fastest muscle contraction velocity in this simulation was approximately ________ mm/msec.

43. True or False:  A muscle that is contracting isometrically will fatigue much slower than one that is contracting isotonically.

44. If you were using your biceps muscles to curl a 7kg dumbbell, when would your muscles be contracting isotonically?

45. Explain why the latent period became longer as the load became heavier in the experiment.

46. Explain why the shortening velocity became slower as the load became heavier in this experiment.

47. Explain why it would take you longer to perform 10 repetitions lifting a 10kg weight than it would to perform the same number of repetitions with a 5kg weight.

48. Describe what would happen in the following experiment:  A 2.5g weight is attached to the end of the isolated whole skeletal muscle used in these experiments.  Simultaneously, the muscle is maximally stimulated by 8.5 volts and the platform supporting the weight is removed. 
a. Will the muscle generate force?
b. Will the muscle change length?
c. What is the name for this type of contraction?



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awesome! thank you so much! Happy



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Oh no! Why can't I view the attachment? Sad



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1.   True or False:  The primary reason for muscle fatigue is the buildup of Ca2+ ions in the muscle fiber.
2.   If an intervening rest period is imposed on active muscle,
a.   it will then be able to generate much more force.
b.   the development of fatigue will be delayed.     
c.   muscle hypertrophy can be prevented.
d.   muscle atrophy can be prevented.
3.   When a skeletal muscle fatigues, what happens to the contractile force over time? 
4.   What are some proposed causes of skeletal muscle fatigue?
5.   Turing the stimulator off allows a small measure of muscle recovery.  Thus, the muscle will produce more force for a longer time period if the stimulator is briefly turned off than if the stimuli were allowed to continue without interruption.  Explain why this might occur.
6.   List a few ways that humans could delay the onset of fatigue when they are vigorously using their skeletal muscles.



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First time user...  I hope someone can tell me how this work...  In need of some help, but I also can help with what I know...  Thanks!!!



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2: Exercise Skeletal Muscle Physiology:
Activity 7: Isotonic Contractions and the Load-Velocity Relationship
Lab Report Pre-lab
1. During an isotonic concentric contraction, the:
b. force generated by the muscle is greater than the weight of the attached load.
2. During an isotonic concentric contraction
b. the latent period increases with heavier loads.
3. During the latent period for an isotonic concentric contraction:
c. cross bridges cycle and, when muscle tension exceeds the load, muscle shortening occurs. 4. Muscle shortening velocity
a. decreases with heavier loads.
5. An isotonic contraction of a muscle is one in which
a. the length of the muscle changes.
Experiment Results Predict Question:
Predict Question:
1.    As the load on the muscle increases, what will happen to the latent period, the shortening velocity, the distance that the weight moves, and the contraction duration?
b. The latent period will increase, the shortening velocity will decrease, the distance will decrease, and the contraction duration will decrease.
Stop & Think Questions:
1.    What kind of contraction did you observe when you attached 2.0 the gram weight to the skeletal muscle and stimulated a contraction?
c. isometric
Post-lab Quiz Results
1.   Which of the weights allowed the fastest muscle shortening velocity?
a. 0.5-g weight
2. Which of the weights induced the longest latent period of the muscle contraction?
c. 1.5-g weight
3. Which weight did the muscle contraction move the greatest distance?
a. 0.5-g weight
4. Which of the weights allowed the longest duration of muscle contraction?
a. 0.5-g weight
5. An isotonic contraction of a muscle is one in which
a. the length of the muscle changes.
6. When lifting a heavy load
d. the muscle shortening velocity is decreased in comparison with lighter loads.



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1.   True or False:  The primary reason for muscle fatigue is the buildup of Ca2+ ions in the muscle fiber.
2.   If an intervening rest period is imposed on active muscle,
a.   it will then be able to generate much more force.
b.   the development of fatigue will be delayed.     
c.   muscle hypertrophy can be prevented.
d.   muscle atrophy can be prevented.
3.   When a skeletal muscle fatigues, what happens to the contractile force over time? 
4.   What are some proposed causes of skeletal muscle fatigue?
5.   Turing the stimulator off allows a small measure of muscle recovery.  Thus, the muscle will produce more force for a longer time period if the stimulator is briefly turned off than if the stimuli were allowed to continue without interruption.  Explain why this might occur.
6.   List a few ways that humans could delay the onset of fatigue when they are vigorously using their skeletal muscles.



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3 years ago

thanks!



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3 years ago

Very helpful!!



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3 years ago

I just found this website by accident. Wow, thanks for such a fantastic site. I just saw Josh posted a download link for the answers to exercise 2. How do I get a good post that I will be able to download it?

Thank you!



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