Calcium and the role of motoneuronal doublets in skeletal muscle control

Bjørn Gilbert Nielsen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

This work presents a novel structural model of skeletal muscle activation, providing a physiologically based account of frequency-dependent muscle responses like the catch-like effect. Numerous Ca2+ reservoirs within muscle fibers are considered, and a simplified analysis of the allocation of Ca2+ resources and the dynamics of calcium transport is proposed. The model correctly accounts for catch-like effects in slow and fast-twitch fibers during long-train stimulations and force-frequency relations in different muscle types. Results obtained from the model compare favorably to experiments showing that prolonged increases in force characteristic of the catch-like effect are not accompanied by sustained increases in free myoplasmic Ca2+. Also, in agreement with early experiments, the interspike interval in catch-inducing doublets is seen to be an important parameter for regulating the precise onset amplitude of the catch-like effect. This suggests that a plausible physiological function for the inclusion of doublets or the exclusion of individual spikes within a regular motor-neuronal spike-train is to rapidly bring skeletal muscles to predefined target forces according to prespecified motor programs in the central nervous system. This is a potentially very useful property directly mediated by the catch-like process modeled here. One further prediction of the model is that the slope of the frequency-tension profile of a given muscle is highly sensitive to changes in the efficiency and temporal characteristics of the dihydropyridine-ryanodine receptor complex. Interestingly, this is consistent with findings made on cardiac muscles, and might incidentally explain some instances of cardiac failure.
Original languageEnglish
JournalEuropean Biophysics Journal
Volume38
Issue number2
Pages (from-to)159-173
ISSN0175-7571
DOIs
Publication statusPublished - 2009

Keywords

  • Force-frequency relation
  • Preprogrammed muscle activation
  • Motoneuronal doublets
  • Excitation-contraction coupling

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