Workshop on Biomechanics and Chemotaxis, Fri, 14 Dec, 2007
Speaker: Jonas Stålhand
Abstract
Smooth muscles cells are found in hollow organs like the vascular system, the iris in the eye, the gastrointestinal tract, and the urinary bladder. The role of smooth muscle is to provide structural integrity to the organ and to allow for active regulation of the geometry and material properties. In addition, the unique ability of smooth muscle to maintain an isometric force at a low energy expenditure allows for the vascular wall to be under constant contraction. This basal tone is an important factor for reducing the transmural stress gradient in the wall.
Smooth muscle contraction can be described by the sliding-filament theory where activated myosin heads, so called cross-bridges, attach to actin and move the filaments relative to each other. The active stress produced by a smooth muscle is related to the number of attached cross-bridges and the overlap of the filaments. The fraction of attached cross-bridges can be described by a calcium-ion dependent kinetic model for the actin-mysoin interaction and the filament overlap is a function of the cell deformation. This highlights an important aspect of smooth muscle contraction: it is a coupled mechanochemical problem.
This presentation will focus on a method that includes both the chemical and mechanical states in the same thermodynamical framework. The governing equations are derived by defining state variables for the chemical and mechanical states and by applying classical balance principles of mechanics. The active and passive stress becomes dependent on a free energy, and by choosing the free energy in a particular way, it can be shown that our model includes a recently proposed and celebrated model for smooth muscle contraction in the limit of small, linear deformations.
URL: www.ricam.oeaw.ac.at/specsem/ssqbm/participants/abstracts/index.php
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