What are the types of myofilaments?

There are three different types of myofilaments: thick, thin, and elastic filaments. 

Thick Filaments

Thick filaments are composed primarily of myosin II, a type of protein. Each thick filament is approximately 15 nm in diameter and made up of several hundred myosin molecules. 

Thin Filaments

Thin filaments are composed primarily of filamentous F-actin, a type of the protein actin. They also contain tropomyosin and troponin. Each F-actin strand is approximately 7 nm in diameter and made up of a chain of globular G-actin subunits. 

Elastic filaments

Elastic filaments are composed of a large elastic protein called titin. Each elastic filament is about 1 nm in diameter. Elastic filaments run through the core of individual thick filaments, stabilizing the filament and centering it between the thin filaments. It also plays a vital role in preventing the thick filament from overstretching.