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Elevation
of [Ca2+]SR can cause increased spark and transient KCa
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frequency that
should lead to membrane hyperpolarization, decrease in
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voltage-dependent
Ca2+ channel activity, reduction in global [Ca2+]i
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and dilation.
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May also increase
the driving force for sarcolemma extrusion
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mechanisms that
are located in the vicinity of the release site, such as
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Na+-Ca2+
exchanger and Ca2+-ATPase.
May also inactivate
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sarcolemmal
voltage dependent Ca2+ channels.
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“Superficial
buffer barrier hypothesis- Ca2+ entering SMC is buffered
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by the SR and is
discharged vectorially towards the sarcolemma,
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without any
effect on global [Ca2+]i.
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