• Author / Uploaded
• Emi Camacho

Citation preview

2/12/2020

PhysioEx Exercise 2 Activity 7

PhysioEx Lab Report Exercise 2: Skeletal Muscle Physiology Activity 7: Isotonic Contractions and the Load-Velocity Relationship Name: Emiliana Camacho Date: 12 February 2020 Session ID: session-1c57c27a-96b4-2f39-6edc-5828e6b2074b

Pre-lab Quiz Results You scored 100% by answering 5 out of 5 questions correctly. 1 During an isotonic concentric contraction, the You correctly answered: force generated by the muscle is greater than the weight of the attached load. 2 During an isotonic concentric contraction You correctly answered: the latent period increases with heavier loads. 3 During the latent period for an isotonic concentric contraction You correctly answered: cross bridges cycle and, when muscle tension exceeds the load, muscle shortening occurs. 4 Muscle shortening velocity You correctly answered: decreases with heavier loads. 5 An isotonic contraction of a muscle is one in which You correctly answered: the length of the muscle changes.

Experiment Results Predict Question 1 Predict Question: 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? Your answer: The latent period will increase, the shortening velocity will decrease, the distance will decrease, and the contraction duration will decrease. https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/

1/5

2/12/2020

PhysioEx Exercise 2 Activity 7

Stop & Think Question 1 What kind of contraction did you observe when you attached the 2.0 gram weight to the skeletal muscle and stimulated a contraction? You correctly answered: isometric. Experiment Data Voltage (v)

Length (mm)

Weight (g)

Velocity* Distance Time Time Twitch (mm/ms) Lifted (contracting)(relaxing) Duration (mm) (total)

8.5

75

0.5

0.100

4.0

40.00

38.00

78.00

8.5

75

1.0

0.057

2.0

35.00

14.00

49.00

8.5

75

1.5

0.022

0.5

23.00

7.00

30.00

8.5

75

2.0

0.000

0.0

0.00

0.00

0.00

*Distance divided by time (contracting).

weight = 0.5 g duration of twitch = 78.00 msec velocity = 0.100 mm/msec distance lifted = 4.0 mm

weight = 1.0 g duration of twitch = 49.00 msec velocity = 0.057 mm/msec distance lifted = 2.0 mm

weight = 1.5 g duration of twitch = 30.00 msec velocity = 0.022 mm/msec https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/

2/5

2/12/2020

PhysioEx Exercise 2 Activity 7

distance lifted = 0.5 mm

weight = 2.0 g duration of twitch = 0.00 msec velocity = 0.000 mm/msec distance lifted = 0.0 mm

Post-lab Quiz Results You scored 100% by answering 6 out of 6 questions correctly. 1 Which of the weights allowed the fastest muscle shortening velocity? You correctly answered: 0.5-g weight. 2 Which of the weights induced the longest latent period of the muscle contraction? https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/

3/5

2/12/2020

PhysioEx Exercise 2 Activity 7

You correctly answered: 1.5-g weight. 3 Which weight did the muscle contraction move the greatest distance? You correctly answered: 0.5-g weight. 4 Which of the weights allowed the longest duration of muscle contraction? You correctly answered: 0.5-g weight. 5 An isotonic contraction of a muscle is one in which You correctly answered: the length of the muscle changes. 6 When lifting a heavy load You correctly answered: the muscle shortening velocity is decreased in comparison with lighter loads.

Review Sheet Results 1 If you were using your bicep muscles to curl a 7-kg dumbbell, when would your muscles be contracting isotonically? Your answer: There are two parts to a bicep curl: raising the arm from the down position and extending the arm downward so it's mostly straight. During both of these movements the muscles are contracting isotonically. 2 Explain why the latent period became longer as the load became heavier in the experiment. How well did the results compare with your prediction? Your answer: My prediction was correct. The latent period became longer. This is because it takes more time to generate the force required. 3 Explain why the shortening velocity became slower as the load became heavier in this experiment. How well did the results compare with your prediction? Your answer: My prediction was correct. The shortening velocity decreased because the heavier the weight, the slower the muscle lifts the weight. https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/

4/5

2/12/2020

PhysioEx Exercise 2 Activity 7

4 Describe how the shortening distance changed as the load became heavier in this experiment. How well did the results compare with your prediction? Your answer: My prediction was correct. The shortening distance decreased as the load got heavier. 5 Explain why it would take you longer to perform 10 repetitions lifting a 10-kg weight than it would to perform the same number of repetitions with a 5-kg weight. Your answer: Because with the 5 kg weight, both the latent velocity and the shortening velocity are quicker than with the 10 kg weight. 6 Describe what would happen in the following experiment: A 2.5-g 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. Will the muscle generate force? Will the muscle change length? What is the name for this type of contraction? Your answer: The muscle will generate force. The muscle would change length. The contraction type is isometric.

https://media.pearsoncmg.com/bc/bc_0media_ap/physioex/10/ex2/act7/

5/5