Experimental Brain Research

, Volume 23, Issue 3, pp 279–291 | Cite as

The tendon organs of cat soleus: Static sensitivity to active force

  • E. K. Stauffer
  • J. A. Stephens
Article

Summary

The static force sensitivity of soleus tendon organ (Ib) afferents has been studied by noting their responses to graded force development produced by isometric contractions of either the whole muscle or single motor units. Data included responses of 23 Ib afferents to contraction of 8 whole muscles (8 experiments) and 16 Ib afferents to contraction of 30 motor units (5 experiments). Tendon organ responses of varying magnitude to contraction of the whole muscle or several of its individual motor units could be explained by differences in the number of muscle fibers that insert into each receptor's capsule and by differences in the contraction strength of these fibers. This finding suggests that soleus tendon organs have similar absolute sensitivities to static force development. An estimate was made of this absolute sensitivity and the value obtained (314 pps/g of force actually coupled to the receptor) is 2 orders of magnitude greater than those previously reported indices that simply relate Ib firing rate to force as measured at the tendon. The relationship between force exerted on a tendon organ's capsule and Ib firing rate is shown to be curvilinear and in keeping with a possible saturation effect that reduces the receptor's responsiveness to active contractions at relatively long muscle lengths.

Key words

Tendon organs Static force sensitivity Motor units Contraction strength Cat 

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References

  1. Barker, D.: Morphology of muscle receptors. In: Handbook of Sensory Physiology, (Ed. C.C. Hunt), Vol. III/2. Berlin-Heidelberg-New York: Springer 1974Google Scholar
  2. Burke, R.E., Tsairis, P.: Anatomy and innervation ratios in motor units of cat gastrocnemius. J. Physiol. (Lond.) 234, 749–765 (1973)Google Scholar
  3. Burke, R.E., Levine, D.N., Salcman, M., Tsairis, P.: Motor units in cat soleus muscle: Physio logical, histochemical and morphological characteristics. J. Physiol. (Lond.) 238, 503–514 (1974)Google Scholar
  4. Gans, C., Bock, W.J.: The functional significance of muscle architecture — a theoretical analysis. Ergebn. Anat. Entwickl.-Gesch. 38, 115–142 (1965)Google Scholar
  5. Henneman, E., Olson, C.B.: Relations between structure and function in the design of skeletal muscles. J. Neurophysiol. 28, 581–598 (1965)Google Scholar
  6. Houk, J.C., Henneman, E.: Responses of Golgi tendon organs to active contractions of the soleus muscle of the cat. J. Neurophysiol. 30, 466–481 (1967)Google Scholar
  7. Houk, J.C., Simon, W.: Responses of Golgi tendon organs to forces applied to muscle tendon. J. Neurophysiol. 30, 1466–1481 (1967)Google Scholar
  8. Houk, J.C., Singer, J.J., Henneman, E.: The adequate stimulus for Golgi tendon organs with observations on the mechanics of the ankle joint. J. Neurophysiol. 34, 1051–1065 (1971)Google Scholar
  9. Jansen, J.K.S., Rudjord, T.: On the silent period and Golgi tendon organs of the soleus muscle of the cat. Acta physiol. scand. 62, 364–379 (1964)Google Scholar
  10. Rack, P.M., Westbury, D.R.: The effects of length and stimulus rate on tension in the iso metric cat soleus muscle. J. Physiol. (Lond.) 204, 443–460 (1969)Google Scholar
  11. Reinking, R.M., Stephens, J.A., Stuart, D.G.: The tendon organs of cat medial gastro cnemius: Significance of motor unit type and size for the activation of Ib afferents. J. Physiol. (Lond.) (In press, 1975)Google Scholar
  12. Stauffer, E.K.: Physiological analysis of motor unit-tendon organ anatomy. Anat. Rec. 181, 486 (1975)Google Scholar
  13. Stauffer, E.K.: The tendon organs of cat soleus: Static and dynamic responsiveness during isometric and anisometric contractions. Ph.D. dissertation. Tucson, Arizona: University of Arizona 1974Google Scholar
  14. Stauffer, E.K., Stephens, J.A.: Responses of tendon organs to ramp changes of active in-series motor unit force. Proc. 4th Meet. Soc. for Neuroscri., p. 435, St. Louis 1974Google Scholar
  15. Stephens, J.A., Reinking, R.M., Stuart, D.G.: The tendon organs of cat medial gastrocnemius: Responses to active and passive forces as a function of muscle length. J. Neurophysiol. (In press, 1975)Google Scholar
  16. Stuart, D., Goslow, G.E., Mosher, C.G., Reinking, R.M.: Stretch responsiveness of Golgi tendon organs. Exp. Brain Res. 10, 463–476 (1970)Google Scholar
  17. Stuart, D., Mosher, C.G., Gerlach, R.L., Reinking, R.M.: Mechanical arrangement and trans ducing properties of Golgi tendon organs. Exp. Brain Res. 14, 274–292 (1972)Google Scholar

Copyright information

© Springer-Verlag 1975

Authors and Affiliations

  • E. K. Stauffer
    • 1
    • 2
  • J. A. Stephens
    • 1
  1. 1.Department of PhysiologyCollege of Medicine, University of ArizonaTuesonUSA
  2. 2.Department of PhysiologyUniversity of Minnesota-Duluth School of MedicineDuluthUSA

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