Chapter 6. Light Diffraction of Cardiac Muscle: Sarcomere Motion During Contraction

  1. Ruth Porter and
  2. David W. Fitzsimons
  1. Rashid Nassar,
  2. Andres Manring and
  3. Edward A. Johnson

Published Online: 30 MAY 2008

DOI: 10.1002/9780470720066.ch6

Ciba Foundation Symposium 24 - Physiological Basis of Starling's Law of the Heart

Ciba Foundation Symposium 24 - Physiological Basis of Starling's Law of the Heart

How to Cite

Nassar, R., Manring, A. and Johnson, E. A. (1974) Light Diffraction of Cardiac Muscle: Sarcomere Motion During Contraction, in Ciba Foundation Symposium 24 - Physiological Basis of Starling's Law of the Heart (eds R. Porter and D. W. Fitzsimons), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/9780470720066.ch6

Author Information

  1. Laboratory of Cardiac Cell Physiology, Department of Physiology, Duke University Medical Center, Durham, North Carolina

Publication History

  1. Published Online: 30 MAY 2008
  2. Published Print: 1 JAN 1974

ISBN Information

Print ISBN: 9789021940250

Online ISBN: 9780470720066

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Keywords:

  • cardiac muscle;
  • light diffraction;
  • contraction;
  • sarcomere motion;
  • papillary muscles

Summary

The technique of light diffraction has been used to measure sarcomere spacing in resting and contracting cardiac muscle. We chose trabeculae (50–100 m̈m in diameter) of frog atrium which were relatively free:of bifurcations and rich in contractile material. The preparation was immersed in frog Ringer at 20–22°C. A small beam (50 m̈m diameter) of monochromatic light (He-Ne laser) illuminated the trabeculae. The distance between the two first-order maxima of the diffraction pattern was sampled at rates up to 60 Hz and a record of local sarcomere motion was constructed. Overall developed and resting tension were also measured. At any given overall length, the resting sarcomere spacing was different at different points along the strand. Sarcomeres were found to shorten significantly (up to 1 m̈m) at various muscle lengths even though the muscle was held isometrically. Sarcomere length-overall force relations were determined at various initial sarcomere lengths, both before and after various inotropic interventions. A comparison between overall tension and sarcomere shortening in these circumstances provides insight into the mechanism underlying Starling's law of the heart.