Mathematical aspects of the cross-bridge mechanism in muscle contraction

1983 ◽  
Vol 7 (6) ◽  
pp. 661-683 ◽  
Author(s):  
Valeriano Comincioli ◽  
Alessandro Torelli
Keyword(s):  
Muscle Contraction ◽  
Cross Bridge ◽  
The Cross ◽  
Cross Bridge Mechanism

Isometric tension and instantaneous stiffness in amphibian skeletal muscle exposed to solutions of increased tonicity

1977 ◽  
Vol 55 (5) ◽  
pp. 1208-1210 ◽  
Author(s):  
Bernard H. Bressler
Keyword(s):  
Mechanical Response ◽  
Current Model ◽  
Ringer Solution ◽  
Isometric Tension ◽  
Bathing Solution ◽  
Cross Bridge ◽  
The Cross ◽  
Cross Bridges ◽  
Cross Bridge Mechanism ◽  
Tetanic Tension

The instantaneous elasticity and maximum isometric tetanic tension of isolated frog and toad sartorii have been measured in hypertonic Ringer solution. Although the mechanical response of contracting muscle continued to decrease as the tonicity of the bathing solution was increased to 1.26 × R, 1.52 × R, and 2.04 × R, a similar change in the instantaneous stiffness could not be shown. This finding was not expected on the basis of our current model of the cross-bridge mechanism which predicts that the instantaneous stiffness is a measure of the total number of tension-generating cross-bridges formed in a stimulated muscle. The compatability of our findings with an electrostatic theory of the cross-bridge mechanism proposed by Iwazumi (1970) is discussed.

scholarly journals Contraction transients of skinned muscle fibers: effects of calcium and ionic strength.

1978 ◽  
Vol 72 (5) ◽  
pp. 701-715 ◽  
Author(s):  
J Gulati ◽  
R J Podolsky
Keyword(s):  
Ionic Strength ◽  
Muscle Fibers ◽  
Kinetic Properties ◽  
Cross Bridge ◽  
Skinned Muscle ◽  
The Cross ◽  
Cross Bridge Mechanism ◽  
Low Ionic Strength ◽  
Bridge Number ◽  
Steady Force

Calcium and ionic strength are both known to modify the force developed by skinned frog muscle fibers. To determine how these parameters affect the cross-bridge contraction mechanism, the isotonic velocity transients following step changes in load were studied in solutions in which calcium concentration and ionic strength were varied. Analysis of the motion showed that calcium has no effect on either the null time or the amplitude of the transients. In contrast, the transient amplitude was increased in high ionic strength and was suppressed in low ionic strength. These results are consistent with the idea that calcium affects force in skeletal muscle by modulating the number of force generators in a simple switchlike "on-off" manner and that the steady force at a given calcium level is proportional to cross-bridge number. On the other hand, the effect of ionic strength on force is associated with changes in the kinetic properties of the cross-bridge mechanism.

scholarly journals Sarcomere mechanics in striated muscles: from molecules to sarcomeres to cells

2017 ◽  
Vol 313 (2) ◽  
pp. C134-C145 ◽  
Author(s):  
Dilson E. Rassier
Keyword(s):  
Muscle Contraction ◽  
Sarcomere Length ◽  
Muscle Fibers ◽  
Strong Support ◽  
Common Mechanism ◽  
Striated Muscles ◽  
Cross Bridge ◽  
The Cross ◽  
Sliding Filament Theory ◽  
Permeabilized Fibers

Muscle contraction is commonly associated with the cross-bridge and sliding filament theories, which have received strong support from experiments conducted over the years in different laboratories. However, there are studies that cannot be readily explained by the theories, showing 1) a plateau of the force-length relation extended beyond optimal filament overlap, and forces produced at long sarcomere lengths that are higher than those predicted by the sliding filament theory; 2) passive forces at long sarcomere lengths that can be modulated by activation and Ca2+, which changes the force-length relation; and 3) an unexplained high force produced during and after stretch of activated muscle fibers. Some of these studies even propose “new theories of contraction.” While some of these observations deserve evaluation, many of these studies present data that lack a rigorous control and experiments that cannot be repeated in other laboratories. This article reviews these issues, looking into studies that have used intact and permeabilized fibers, myofibrils, isolated sarcomeres, and half-sarcomeres. A common mechanism associated with sarcomere and half-sarcomere length nonuniformities and a Ca2+-induced increase in the stiffness of titin is proposed to explain observations that derive from these studies.

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