Muscles move skeletal parts by contracting Team 1

Contractions The ability to move requires that the muscles be attached to the skeleton in antagonistic pairs When bicep contracts, triceps relax- When triceps contract, biceps relax

The structure of skeletal muscle Muscle fiber consists of a bundle of long fibers running parallel to the length of the muscle Bundle of myofibrils arranged longitudinally

Myofibrils Two kinds of myofilaments : Thin filaments- two strands of actin and one strand of regulatory protein coiled around thick filament Thick filaments- staggered array of myosin

Contractions In a relaxed muscle fiber, the I bands and the H zone are relatively wide During contraction, the thick, and thin filaments slide past each other, reducing the width of the I bands and H zone and shortening the sacromere In a fully contracted muscle fiber, the thin filaments overlap, eliminating the H zone. The I bands disappear as the ends of the thick filaments contract the Z lines

Myosin-Actin interactions underlying muscle fiber contraction See figure 49.30, page 1068 as we explain