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8 Cards in this Set
- Front
- Back
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Conductance of what determines the resting membrane potential in cardiac muscle cells?
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Conductance to K+
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What is the resting membrane potential on the nonpacemaker components of the heart?
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90Mv, which is close to the K+ equilibrium potential
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What maintains the resting membrane potential?
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Na+ K+ ATPase membrane protein
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What does it mean when a membrane depolarizes?
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There is an inward current that brings in positive charge into the cell.
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What does it mean when a membrane hyperpolarizes or repolarizes?
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There is an outward current that removes positive charge from the cell.
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Describe what happens during each of the following phases of a cardiac action potential:
Phase 0 Phase 1 Phase 2 |
Phase 0= Upstroke, caused by a rapid transient increase in Na+ conductance, which allows an inward Na+ current to depolarize the membrane(I-Na)
Phase 1= Brief initial repolarizaztion, caused by an outward K+ current, which is due to both chemical and electrical gradients, and decrease in inward Na+ current due in part to a decrease in Na+ conductance Phase 2= Plateau phase, caused by transient increase in Ca+, conductance and an increase in K+ conductance, which causes inward Ca+ and outward K+ currents(I Ca) |
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Define Phase 3 and 4 of the cardiac action potential.
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Phase 3= Repolarization, caused by decrease in Ca+ conductance and an increase in K+ conductance resulting in a large outward K+ currentI(K+ out).
Phase 4= Resting membrane potential, caused by an equilibrium between outward and inward K+ currents(I K+) |
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What determines the peak of the cardiac action potential?
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Conductance to Na+
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