Biology 304

Skeletal Muscle Lab

What follows are some good tracings of the phenomena investigated over the skeletal muscle lab session.

1. Treppe and Tetanus. What gives rise to the increased contraction strength in treppe? Why does contraction strength then plateau or decrease in size?

 

 

What explains the difference in the shapes of the tracings between incomplete tetanus and complete tetanus? Another example, from a previous year, is shown here. However, use the data from the digital series below for your report. Tracings are not generally included in reports. How would you graph the data shown below?

The series below shows the effect of increasing stimulation frequency on the muscle as recorded by students using the digital recording system.

The times indicated in the column headings is the amount of time between the two vertical blue lines on the tracing.

 

1 pps
ten seconds
5 pps
four seconds
10 pps
three seconds
20 pps
three seconds
40 pps
four seconds
Use a calibration factor of 0.25 V = 1 mm of contraction for this exercise.

 


The calibration. Why did we calibrate the transducers? Use this calibration for the remaining parts of the exercise. For this tracing and all others below which are recorded on the green chart recorder paper, the small divisions are 1 mm square, the largest squares are 1 cm square.

 

 

2. Describe the effect and physiology behind increasing voltages on muscle contraction. A graph would be useful.

Here's a version collected digitally; the dark vertical lines mark the division between trials. Use the previous data set in your lab report, not this one.

3. Muscle twitch and contraction velocity. Here is one figure with the tests for 5 g and 55 g masses:  The chart speed was set to 5 cm/s.

4. Preloading: The results for the preloading 5-85g are found here (test masses in grams): 5 15 25 35 45 55 65 75 85. The chart speed was set to 5 cm/s.

The remaining preloading trials are found here: 95 105 115 125 135 and here 145 155 165 175. The muscle length at each tested mass can be found in this Excel file. How does muscle length vary with load? How do velocity and work vary with load?

The afterloading trials can be found here (use that set for your report) and a different set here. Which condition, afterloading or preloading, allows the muscle to do more work? Why?

 

5b. What are some factors involved in fatigue? How would this tracing be different if we fatigued the muscle in vivo (in the living animal)? Do not include this tracing (or any tracings on this page!) in your report. How would you graph the two series of contractions efficiently?

 

How would you contrast the 2nd bout of muscle contractions with the first?  

 


References

Allen, D. G., Lamb, G. D. and Westerblad, H. 2008. Skeletal Muscle Fatigue: Cellular Mechanisms. Physiol. Rev. 88: 287-332. PDF

Buchthal, F., Guld, C. and Rosenfalck, P. 1955. Propagation velocity in electrically activated muscle fibres in man. Acta Physiol. 34: 75-89. PDF

Büllow, P.M, Nørregaard, J., Danneskiold-Samsøe, B. and Mehlsen, J. 1993. Twitch interpolation technique in testing of maximal muscle strength: Influence of potentiation, force level, stimulus intensity and preload. Eur. J Appl. Physiol. 67: 462-466. PDF

Cooke, R., Franks, K. Luciani, G.B. and Pate, E. 1988. The inhibition of rabbit skeletal muscle contraction by hydrogen ions and phosphate. J. Physiol. 395: 77-97. PDF

Eisenberg, E., Hill, T.L. and Chen, Y. 1980. Cross-bridge model of muscle contraction. Quantitative analysis. Biophys. J. 29: 195-227. PDF

Fenn, W.O. 1923. A quantitative comparison between the energy liberated and the work performed by the isolated sartorius muscle of the frog. J. Physiol. 58: 175-203. PDF

Fitts, R.H. 1994. Cellular mechanisms of muscle fatigue. Physiol Rev. 74: 49–94. full text

Gregory, C.M. and Bickel, C.S. 2005. Recruitment patterns in human skeletal muscle during electrical stimulation. Phys. Ther. 85: 358-364. PDF


Herzog, W. and Ait-Haddou, R. 2002. Considerations on muscle contraction. J. Electromyography and Kinesiology. 12: 425-433. PDF

Hill, A. V. 1953. The mechanics of active muscle. Proceedings of the Royal Society of London. Series B, Biological Sciences. 141: 104-117.  PDF

Minot, C.S. 1878. Experiments on tetanus. J. Anat. Physiol. 12: 297-339. PDF

Rassier, D.E., and Macintosh, B.R. 2002. Length-dependent twitch contractile characteristics of skeletal muscle. Can. J. Physiol. Pharmacol. 80: 993–1000. PDF

Rassier, D.E., Macintosh, B.R., and Herzog, W. 1999. Length dependence of active force production in skeletal muscle. J. Appl. Physiol. 86:1445-1457. PDF

Stehle, R. and Brenner, B. 2000. Cross-bridge attachment during high-speed active shortening of skinned fibers of the rabbit psoas muscle: Implications for cross-bridge action during maximum velocity of filament sliding. Biophys. J. 78:1458 –1473. PDF

Taylor, S.L., Lopez, J.R., Griffiths, P.J., Trube, G. and Cecchi. G. 1982. Calcium in excitation-contraction coupling of frog skeletal muscle. Can. J. Physiol. Pharmacol. 60: 489-502. PDF

Westerblad, H. Allen, D.G. and Lannergren, J. Muscle fatigue: lactic acid or inorganic phosphate the major cause? News Physiol. Sci. 17: 17-21. PDF

 

 

 

 

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R.F. Lauff
Department of Biology
St. Francis Xavier University
Antigonish, NS Canada B2G 2W5