1. Mr. Whedon Wed 7:25 By: Marc Magliaro Deisy Maguirre Shquanda Meylor

2. 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.

3.  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.

4.  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.

5. 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.

6.  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.

7. 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

8.  The A band includes a thickening which is know as the M- Line, which consist of proteins that help hold the thick filaments place.

9.  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.

10.  A singel sarcomere extends from one Z line to the other Z line.

11. 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.

12.  Thick Filaments are composed many molecules of myosin. Each myosin molecules consist of two twisted protein strands called cross-bridges.

13.  Thin filaments consist of double strands of actin twisted.  Thin Filaments also consist of two typs of protein troponin and tropomyosin.