PT - JOURNAL ARTICLE AU - Yuri Kamnev TI - Frank-Starling law and Bowditch phenomenon may have the common theoretical grounds AID - 10.1101/069609 DP - 2016 Jan 01 TA - bioRxiv PG - 069609 4099 - http://biorxiv.org/content/early/2016/08/15/069609.short 4100 - http://biorxiv.org/content/early/2016/08/15/069609.full AB - Formalized description of heterometric and homometric regulation was obtained while modeling of circulation on the basis of several principles; the leading one is defined as follows: concept of circulation presumes that the part of pressure which ventricle produces for propelling of blood must be left, as guaranteed part, for producing of deformation of the next ventricular filling. The relationship between the force of contraction, F, and linear deformation, L, was deduces as function F = f(L2) which does not deny approximation to direct proportionality at the operating region of Frank-Starling law (ascending limb cut out from parabola). Another function determines the force of contraction when the sizes of deformation drop below the domain of Frank-Starling function: F = f(1/tsyst), where tsyst is the duration of systole. Bowditch staircase is explained as repeated (cyclic) transitions from one function to another because “a resting muscle” (condition of Bowditch experiment) can be equalized with too small deformations (below the limit of domain of Frank-Starling function).