16 - 1 spindle shape single nucleus small size(20 x 400 µm...

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Sheet1 Page 1 Excitation-contraction coupling - smooth muscle cells can be activated by synaptic transmission from autonomic neuronal fibe r s If the muscle cells are activated independently by neuronal input they are referred to as multi-unit smooth muscle. Examples i n Smooth muscle cells capable of self-excitation are coupled into a functional syncytium by means of gap-junctions and exhibit p 2 forms of self-excitation: (Figure 8-31) pacemaker potential - Gradual depolarization until threshold is reached slow-wave potential - Alternating depolarizing and hyperpolarizing swings in membrane potential Smooth muscle structural characteristics (Table 8-3)
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Unformatted text preview: 1) spindle shape, single nucleus, small size (20 x 400 µm), arranged in sheets 2) long thick myosin filaments 3) thin actin filaments that contain tropomyosin, but lack troponin 4) contain intermediate filaments for structural support 5) lack sarcomere organization, but contain dense bodies that act as anchors 6) lack T-tuble organization of the plasma membrane 7) poorly developed sarcoplasmic reticulum 8) 10-15 thin filaments for each thick filament, oriented diagonally 9) contraction of the filament lattice causes cellular shortening and expansion...
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