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15 Cards in this Set
- Front
- Back
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What two types of channels cause action potential in cardiac muscle?
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fast sodium and slow sodium-calcium channels
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What channel is responsible for causing the plateau?
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slow sodium-calcium channels
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the loss of what ion returns the membrane back to resting potential?
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K
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what is the normal refractory period of the ventricle
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.25 to .30 second
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what is the refractory period for the atria?
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0.15
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The strength of contraction depends on the concentration of what ion?
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the concentration of Calcium in the ECF
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what is the role of calcium ions in the cytoplasm?
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to interact with troponin and stimulate cross bridge formation --> promote the sliding of the actin and myosin filaments along one another
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when heart rate increases, the cardiac cycle _____.
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decreases
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What part of the cardiac cycle decreases the most with an increase in the heart rate?
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The diastole decreases by the greatest percentage --> the heart does not stay relaxed long enough to allow complete filling
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How much does Atrial contraction increase the ventricular pumping effectiveness?
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20%
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When does the v wave occur?
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The v wave occurs toward the end of ventricular contraction, resulting from slow flow of blood into the atria from the veins while the AV valves are closed
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What is the cause of the c wave?
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The c wave occurs when the ventricle contracts, it is partly caused by slight backflow of blood into the atria but mainly by bulging of the AV valve backward toward the atria due to increasing pressure in the ventricles
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Why is there a period of isometric contraction?
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This occurs immediately after ventricular contraction starts and the AV valves have closed and the ventricles are building up enough pressure to push the semilunar valves open
there is contraction but no emptying |
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Why is there a period of isometric relaxation
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At the end of systole, there is ventricular relaxation that allows the ventricular pressure to decrease rapidly. The decrease in pressure allows the Semilunar valves to slam shut with the back pressure from the great vessels. At this point there is no change in the ventricular volume as the ventricles continue to relax
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Why do the papillary muscles contract when the ventricles contract
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they pull the vanes of the valves inward toward the ventricles to prevent their bulging too far backward toward the atria
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