Physical Chemistry of Contractile Process in Muscle

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Abstract
The physico-chemical model of the contractile mechanism is used to interpret the thermal phenomena in tetanized muscle. The constant heat of maintenance is due to the heats of the reactions coupled with the reactions LS in the steady state cycle. A quantitative expression for the heat of maintenance is derived. The physico-chemical model predicts that the heat of maintenance should pass through a maximum at some particular length. This prediction is in agreement with exptl. results. The theory predicts high temp, coeffs. for the rate of development of tension, and the speed of shortening, a low temp, coeff. for the developed tension and a negative temp, coeff. for the economy of the muscle. These predictions are in agreement with exptl. observations. A tentative interpretation is offered of the high economy of some muscles and of the "catch mechanism." The thermal phenomena in a twitch and their temp. coeffs. are examined, and both the similarities and the dissimilarities to the thermal phenomena in a tetanus are interpreted in terms of the physicochemical model. The heat of shortening is interpreted as the thermal manifestation of the increase in the rate of the shortening reaction. The absence of the negative heat of lengthening is interpreted in terms of the kinetics of the 2 concurrent reactions. The kinetics of the 2 reactions is also used to interpret the Fenn effect.

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