Caption: Heart muscle cell; nucleus, mitochondria, actin / myosin fibers, A bands, I bands and Z lines. Cardiac muscle, unlike skeletal muscle, is composed of separate cellular elements. A cardiac muscle cell has a large nucleus (green tip only) and numerous mitochondria (red). The high concentration of mitochondria reflects the large energy demands of predominant the heart. Contractile proteins of actin and myosin myofilaments are in the cytoplasm. They form bands (sarcomeres) of varying density: A bands - pink, I bands - light yellow, Z lines - green. The Z lines are regions with dense protein disks. The heart produces regular electrical impulses causing the muscle myofibrils to slide over one another and contract the cardiac muscle.
Magnification*: x5, 050
Type: TEM
Copyright 1999 Dennis Kunkel Microscopy, Inc.
Keywords: 1974A,muscle,heart,cardiac,mitochondria,mitochondrion,actin,myosin,sarcomere,A band,I band,Z line,TEM,animal cell,actin filament,actin filaments,actomyosin,actomyosin filaments,myofibril,myofibrils,myosin filament,myosin filaments,sarcomeres