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21 Cards in this Set
- Front
- Back
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What are the two types of cardic cells?
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working
specialized |
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Describe working cardiac cells:
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well organized myofibrils, no pacemaker activity, very abundant
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Describe specialized cardiac cells:
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poorly organized myofibrils, not very abundant, pacemaker activity, coordinate muscular contraction
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Where are specialized cardiac cells located?
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SA/AV nodes, R/L bundle branches, AV bundle
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What is the only electrical connection between the atrium and the ventricle?
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AV bundle (His bundle)
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What structure slows the impulse for ventricular contraction to allow time for the atria to empty blood into ventricles?
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AV node
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what is the purpose of Purkinje fibers?
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interact with the working muscles (help pass along electrical impulses)
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What ion are the resting membranes permeable to and what is this significance?
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K+ (flow in = flow out)
this creates an electrical gradient across the membrane of -80 to -90 mV. |
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Why does the measured membrane potential (-80 mV) deviate from the predicted potential (-120mV)?
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a small amount of Na+ is constantly leaking into the cell, making the membrane potential more pos. since the equilibrium potential of Na+ is +70 mV.
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What is the approximate equilibrium potential of Ca2+?
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+120 mV
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what is the equilibrium potential equation?
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E(X)(mV) = -60log [x(i)]/[x(o)]
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what causes the cell membranes to depolarize?
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Influx of Na+ into the cell.
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What are the 4 stages of the action potential per beat of the heart?
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0: depolarization
1: initial repolarization 2: plateau phase 3: rapid repolarization |
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During which stage of the AP is K+ least permeable? What is this called and explain why it occurs?
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stage 0: depolarization.
anomalous rectification (EDIT) |
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What is the fast channel during the AP of a cardiac cell?
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Na+ channel
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What causes the slow response of the cardiac cell action potential?
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Ca2+ channel (influx)
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what is the purpose of the Ca2+ influx during the AP? and when do these channels open?
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opening of Ca2+ channels contribute to plateau phase because their conductance lasts longer than that of Na+. Thus the influx of Ca2+ contributes to mm con't. These channels open right after Na+ channels open (depol.)
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How long are the AP's of a cardiac cell? Nerve cell?
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cardiac: 300-400 msec
nerve: 1-2 msec |
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What is the equ. for Ohm's law? and what does it calculate?
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I(i) = g(i)[E(m)-E(i)]
calculates: current of an ion across a membrane |
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What is the relative refractory period?
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a short refractory period when mm fiber is not completely recovered and cannot respond to new stimuli
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where does the slow response from the Ca2+ channels occur?
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in the SA and AV nodes
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