Muscle Contraction

Muscle cells are designed to generate force and movement. There are three types of mammalian muscles-skeletal, cardiac, and smooth. Skeletal muscles are attached to bones and move them relative to each other. Cardiac muscle comprises the heart, which pumps blood through the vasculature. Skeletal and cardiac muscles are known as striated muscles, because the filaments of actin and myosin that power their contraction are organized into repeating arrays, called sarcomeres, that have a striated microscopic appearance. Smooth muscle does not contain sarcomeres but uses the contraction of filaments of actin and myosin to constrict blood vessels and move the contents of hollow organs in the body. Here, we review the principal molecular organization of the three types of muscle and their contractile regulation through signaling mechanisms and discuss their major structural and functional similarities that hint at the possible evolutionary relationships between the cell types. Outline 1 Introduction 2 The sarcomere of striated muscles 3 Thin filaments 4 Regulation of striated muscle contraction resides on the thin filament 5 Thick filaments 6 Myosin isoforms of muscle 7 Titin 8 Actin -myosin interactions within the sarcomere 9 Z-and M-lines function as cross-linking regions 10 Force transmission 11 Signaling roles of the sarcomere 12 Differences between cardiac and skeletal muscle 13 Differences between striated and smooth muscle 14 Conclusion