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Cards In This Set
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Smooth muscle characteristics
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Single central nucleus; corkscrew shaped if contractedactin/myosin filaments that are NOT striateddense bodies anchoring thick and thin filaments to sarcolemma
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How is contraction propagated from cell to cell in smooth muscle?
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Gap junctions
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What does smooth muscle form in the gut?
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Muscularis externa, with inner circular and outer longitudinal layers
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Characteristics of the inner circular layer of muscularis externa
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Thicker, tight spiralcompresses and mixes by constricting lumen sizemany gap junctions --> syncytium
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Characteristics of the outer longitudinal layer of muscularis externa
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Thinner, loose spiralpropels contents by shortening the tubefewer gap junctions
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Layer b/w the layers of muscularis externa
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Myenteric plexus: ganglion cells of the postganglionic parasympathetic and enteric nervous system neurons (can't tell the difference b/w them)
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Characteristics of smooth muscle contraction
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Involuntaryfibers usually partially contracted, aka smooth muscle tone
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Mean resting potential of GI smooth muscle
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-60 mV
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Slow waves
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Fluctuations in the membrane potential of the GI smooth muscle with a magnitude of 5-15 mV
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Basal electrical rhythm (BER)
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Frequency of slow waves3-12/minute
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Parts of the GI tract that have BER
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Distal stomach, small intestine, and colon
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Parts of the GI tract that do not have BER
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Esophagus, proximal stomach, most sphincters
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What does spread of the slow wave depend on?
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Gap junctions
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What controls the excitation of the network of smooth muscle?
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Interstitial cells of Cajal
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Spike potentials
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A true action potential that occurs at the peak of a slow wave
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