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23 Cards in this Set
- Front
- Back
What initiates the heartbeat?
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spontaneous depolarization of the SA node
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What are I(f) channels and what ion do they transport?
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funny channels open to Na+ during phase 4 (slow diastolic depolarization)
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How does the autonomic system modulate the rate of SA node firing?
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Sympathetics: decrease the length of phase 4 depolarization by increasing funny channel activity; Parasympathetics: increase the length of phase 4 depolarization by increasing the activity of I(K+) channels and decreasing the activity of funny channels
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What is overdrive suppression of a pacemaker and which pacemaker exhibits this characteristic
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Overdrive suppression is the concept of the fastest pacemaker taking control over the heart rate. The SA node does this in the human heart
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Why is there a delay between atrial contraction and ventricular contraction?
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The 'AV Block'. The AV node conducts action potentials slowly, creating a delay between the atrial and ventricular contractions
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AV nodal conduction is dependent on what type of channels?
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voltage gated Ca++ channels
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What two things prevent re-excitation of the atria via ventricular depolarization?
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annulus fibrosis cordis and AV node refractoriness
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How is the action potential propagated through the ventricular tissue?
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passive current
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What determines if a valve is open or closed?
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the pressure differential across the valve
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What phase of the cardiac cycle is the first part of systole?
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phase 2 - Isovolumetric contraction
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During what phase is ventricular filling complete?
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phase 1b - atrial systole
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What phase is the 'C wave' seen in and what causes it?
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phase 2 - isovolumetric contraction of the ventricles causes the mitral and tricuspid valves to press into the atria, increasing their pressures as well
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During which phase is S1 heard and what causes it?
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phase 2 - isovolumetric contraction, the sound is caused by the slamming shut of the mitral and tricuspid valves
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During what phase does ejection occur?
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phase 3 - ventricular systole
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What phase is the 'V wave' seen in and what causes it?
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phase 3 - ventricular systole, the v wave is caused by blood entering the atria while the mitral and tricuspid valves are still closed, increasing the atrial pressure
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What phase is S2 heard in and what causes it?
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phase 4 - isovolumetric relaxation of the ventricles causes the aortic and pulmonary valves to slam shut
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What is the ejection fraction?
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the percent of the blood volume in the ventricles that is ejected during systole
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During what phase would you hear S3?
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phase 4 - isovolumetric relaxation
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During what phase does passive ventricular filling occur?
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phase 1a
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Label the action of the valves at each point
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At what point in the cardiac cycle would a murmur from aortic stenosis be heard?
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between S1 and S2
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At what point in the cardiac cycle would a murmur caused by aortic incompetence be heard?
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following S2
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At what point in the cardiac cycle would a murmur caused by tricuspid or mitral valve incompetence be heard?
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between S1 and S2
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