Thick filament. (A) An electron micrograph of a reconstituted thick filament reveals the presence of myosin head domains at each end and a relatively narrow central region. A schematic view below shows how myosin molecules come together to form the thick filament. (B) A diagram showing the interaction of thick and thin filaments in skeletal-muscle contraction.

[(A, top) Courtesy of Dr. Hugh Huxley.]