Muscle Tissue n n n Characteristics of Muscle

Muscle Tissue n n n Characteristics of Muscle Responsiveness: to produce chemical signals coordinated with electrical charges Conductivity: to pass stimulus beyond local area to excite contraction Contractility: to shorten when stimulated Extensibility: to stretch between contractions Elasticity: to return to original shape

Skeletal Muscle n Skeletal muscle: voluntary striated muscle attached to one or more bones n Striations: caused by overlapping of contractile proteins

Myofilaments n n n 1. 2. 3. Myofilament: long protein cords, fills muscle cell A myofibril is a bundle of 3 myofilaments Myofilaments: Thick filaments: made of myosin, looks like a golf club Thin Filaments: are composed of two strands of proteins, F actin and G actin where G actin contains active sites where the head of myosin can bind Elastic filaments: made of titin, flanks the thin filament and anchors it to the Z disk

Striations n. A band (d. Ark band): consists of thick filaments that lay side by side n I band (L(I)ght band): consists of thin and elastic filaments between thick filaments n H band: a section of the A band that is not covered with thin and elastic filaments n Z disk: a dense protein that anchors thin and elastic filaments, central to contraction of muscle

Striations n Sarcomere: the functional contractile unit located between the Z disks