  Based on the Stochastic Inclined Rods Model (SIRM) proposed by H. Matsuura
and M. Nakano, we study the microscopic motion of actin myosin system including
the motion of the G-actin. Our model is composed of an inclined spring (rod), a
myosin head, a myosin filament and G-actins. We discuss the stochastic
resonance between the myosin head and random noise. The results of calculation
show that the model can convert the random motion to one directional motion,
and the myosin head works as a resonator of random noise which absorbs the
energy through the stochastic resonance. The intermolecular potential between
the myosin head and G-actin and the inclined rod play a key role for the
muscle's motion. The energy consumed by the motor is directly supplied from the
surroundings (i.e., the thermal motions of water molecules).
