title: Towards bridging the gap from molecular forces to the movement of organisms.
abstract: Muscles are responsible for generating the forces required for the movement of multicellular organisms. Microscopically, these forces arise as a consequence of motor proteins (myosin) pulling and sliding along actin filaments. Current knowledge states that the molecular forces between actin and myosin are linear in nature [Huxley and Simmons (1971) Nature (London) 233, 533-538] and that the physiologically observed non-linearities (e.g. Hill's force-velocity relationship) are a consequence of non-linearities in the attachment/detachment ratios. However, this view has been disputed recently [Nielsen (2002) J. Theor. Biol. 219, 99-119], inspired by results from protein pulling experiments showing that proteins often have non-linear entropic force-extension profiles. Irrespective of the case, the present study aims at integrating such basic force-producing properties into large-scale simulations of muscle, which may accommodate macroscopic properties of muscles, e.g. the catch-like effect, the Henneman principle and accurate twitch force and motor unit size distributions. As a test of the underlying principles, a model of the biceps caput breve muscle is presented and compared with experimental data.
authors.affiliation: Department of Physics, Quantum Protein Centre (QuP), Technical University of Denmark, Bldg. 309, DK-2800 Lyngby, Denmark. bjorn.nielsen@fysik.dtu.dk
authors.forename: B G
authors.initials: BG
authors.lastname: Nielsen
mesh_terms: D000199:Actins / Q000737:chemistry; D000818:Animals; D008954:Models, Biological; D015233:Models, Statistical; D008962:Models, Theoretical; D009068:Movement; D009132:Muscles / Q000378:metabolism / Q000502:physiology*; D009218:Myosins / Q000737:chemistry; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D000199:Actins; D009218:Myosins