Locally and globally coupled oscillators in muscle

Area of Science:

• Muscle physiology
• Biophysics
• Nonlinear dynamics

Background:

• Striated muscle displays autonomous oscillations known as spontaneous oscillations of sarcomeres (SPOC) at intermediate activation levels.
• These oscillations involve sarcomere length changes and manifest as various patterns, including traveling waves, within myofibrils.

Purpose of the Study:

• To investigate the mechanisms underlying the emergence of SPOC patterns in striated muscle.
• To model and understand the role of local and global couplings in generating oscillatory behaviors.

Main Methods:

• Developing a unit model that captures single-sarcomere SPOC characteristics.
• Mechanically connecting these unit models in series to simulate myofibril behavior.
• Reducing the connected model to phase equations to analyze coupling effects.

Main Results:

• The series-connected unit model successfully reproduced the observed SPOC patterns, including traveling waves.
• Mathematical reduction to phase equations highlighted the critical role of combined local and global couplings.
• This revealed the fundamental principles governing the complex oscillatory dynamics in muscle.

Conclusions:

• The mechanical coupling of simple unit models can generate complex SPOC patterns observed in myofibrils.
• The interplay between local and global couplings is essential for the emergence of these muscle oscillations.
• This study provides a framework for understanding muscle contractility dynamics.