Extracellular Calcium needed for cardiac muscle - USMLE Forums
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Old 10-29-2010
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Heart Extracellular Calcium needed for cardiac muscle

FA (256) states, cardiac muscle contraction is dependent on extracellular Calicium !
Is this Plasma Calcium or Interstitium Calcium?
hypocalcemia and hypercalcemia will effect cardiac contraction?
plz explain me the concept!
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Old 10-29-2010
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Question

i think this has to be plasma calcium.not sure.
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Old 10-29-2010
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Info Both the intravascular and the interstitial spaces are extracellular

In contrast to skeletal muscle, the cardiac muscle must use extracellular Calcium to contract (which enters via L-type Calcium channel) in what's called the Calcium activated Calcium release which means that the extracellular Calcium will stimulate the release of the intracellular Calcium stored in the sarcoplasmic reticulum.

In skeletal muscle. the contraction is dependent only on intracellular Calcium which is stored in the sarcoplasmic reticulum.

It doesn't matter whether it's the intersitium or the vascular space, in both spaces it's extracellular.
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