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21 Cards in this Set

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