MUSCLE PHYSIOLOGY

Detailed explanation-1: -Sliding-filament model of muscle contraction. The actin filaments slide past the myosin filaments toward the middle of the sarcomere. The result is shortening of the sarcomere without any change in filament length.

Detailed explanation-2: -The myosin head moves toward the M line, pulling the actin along with it. As the actin is pulled, the filaments move approximately 10 nm toward the M line. This movement is called the power stroke, as it is the step at which force is produced.

Detailed explanation-3: -7. What causes actin to slide toward the center of the sarcomere? A: An increase in pressure on the distal end of actin from the transverse tubule forces the actin to move toward the center of the sarcomere.

Detailed explanation-4: -The sliding can only occur when myosin-binding sites on the actin filaments are exposed by a series of steps that begins with Ca++ entry into the sarcoplasm. Tropomyosin is a protein that winds around the chains of the actin filament and covers the myosin-binding sites to prevent actin from binding to myosin.