9.3.-2 Chapter Human Structure and Function

Structure of actin

Made of globular actin, each with myosin-building site, and tropomyosin and troponin proteins

Structure of myosin

6 polypeptide chains, 4 light and 2 heavy that twist into a tail

Sarcoplasmic Reticulum

Intracellular tubule, regulates intracellular levels of ionic calcium, stores calcium and releases it when stimulated

Terminal cisterns

Sarcoplasmic Reticulums that form cross channels at A band to I band junctions, occur in pairs

T Tubules

Sarcolemma forms T tubules, at each A to I band junction, form triads in between terminal cisterns

Lumen

Cavity in T tubules that increases muscle fiber’s surface area to allow changes in membrane potential

Sarcolemma

Plasma membrane of muscle fibers

Sarcoplasm

Cytoplasm of muscle fibers

Define Contraction

Activation of myosin’s cross bridges

Which bands shortens in contraction

Distance between Z disc and I band

Cross bridges in contraction

break and form repetitively to form tension