Muscle Contraction (Skeletal)

• Skeletal Muscles are arranged in Antagonistic Groups.
•  Every Muscle is connected on two sides by tendons.
• Muscles are composed of multicellular structures called muscle fibers (visible)
• Muscle Fibers are composed of long multinucleated cells that stretch across the entire muscle.
• Muscle cells are composed of subcellular tubules called Myofirils. Each myofibril is composed of two major protiens called myosin and actin.
• Each myofibril  is divided in structures call sarcrameres which are the structural and functional uint of a muscle.

I The Sacromere- muscles are made up entirely of these structures.
A. When a muscle is relaxed, there is a protien that covers the Actin Binding Sites and this will Not allow teh myosin bonds to bond, so the two fibers, Actin and Myosin will slide freely across one another.
B. However, when an electrical impulse is sent to the muscle, the actin binding sites are exposed, the myosin heads will bond to jthe creating crossbridges.
C. This changes the structure of the myosing head and it will ratchet the actin strand toward the A-Zone. closing the distance between the myosing head and the acting binding site.
D. Once this happends the Myosing head reverts back to it's original structure and position.
E. The head will now find a new actin binding site and the process will continue until:
1The muscle is fully contracted
2 The electrical impulse stops.
3ATP Runs out- cramp, Rigor rigor Mortis:I(Stiffness of Death)