Mr. Whedon Wed 7:25 By: Marc Magliaro Deisy Maguirre Shquanda Meylor
A sarcomere is the basic unit of a Muscle 's cross-striated myofibril. Myofibrils are thread like structure Which consist of two types of protein filaments. Myosin which is a thick filament and Actin which is a thin filament.
The striations form a repeating pattern of units called Sarcomeres along each muscle fiber. Muscle fibers in a way themselves are basically collections of sarcomeres. Myofibrils may be thought of as sacromeres joined end to end.
There are two types of Myofibrils One type is actin which is a thin filament and the other is myosin which is composed of a thick filament. The origination of these filaments produce striation characteristics of skeletal muscle fiber.
There are 2 main parts of the striation pattern The two parts are called I bands and A Bands. The I bands are composed of the Thin filaments (actin) and the A bands are composed of Thick (myosin) and Thin (actin) filaments.
These Actin filaments ( thin) are held by direct attachments to structures called the Z Line. ( Z Band) The Z line is in the center of the I band.
The A Band consist of thick myosin filament overlapping with thin actin filaments. The A band also consist of a region where only thick filaments exist. This regions is called the H-Zone
The A band includes a thickening which is know as the M- Line, which consist of proteins that help hold the thick filaments place.
The H- Zone consist of only thick filaments and is also located in the A band. The H zone may change depending on the degree of filament overlap.
A singel sarcomere extends from one Z line to the other Z line.
Myosin: H Zone Actin: I band Actin and Myosin: A Band Sacomere Endline: Z line which is located in the I Band Sacomere Midline: M line which is located in the H Zone.
Thick Filaments are composed many molecules of myosin. Each myosin molecules consist of two twisted protein strands called cross-bridges.
Thin filaments consist of double strands of actin twisted. Thin Filaments also consist of two typs of protein troponin and tropomyosin.