In: Anatomy and Physiology
The sarcomere of the muscle is made up of many myofilament.
Myofilament are of two types-
1. Actin
2. Myosin
Actin filament are thin filament . These filament extend form either side of the 'Z' line, run across the 'I' band and enter into 'A' band upto the 'H' zone.
Myosin filaments are thick. These filament are situated in 'A ' band.
Some lateral processes called cross bridges arise from each myosin filament. These bridges have enlarged structure called myosin head.
Myosin head attach themselves to actin filament. These head pulls actin filament during contraction of muscle.
During contraction of muscle, the actin filament glides down between the myosin filament towards the centre of 'H' zone and approaches the corresponding actin filament from the next 'Z' line. The 'Z' line also approaches the ends of myosin filaments so that the 'H' zone and 'I' band are shortened during contraction.
During relaxtion, the actin filament and 'Z ' line come back to original position.