AP Test 2 Part 1
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trace the wave of depolarization through the conduction system
SA node to atrial wall to AV node to bundle of HIS to bundle branches to apex to Purkinje fibers to ventricular muscle cells
three functions of the cardiac skeleton?
- structure- to hold open the AV openings
- rigid structure against which the cardiac muscles can contract
- electrical insulation between atria and ventricles
what is the significance of the electrical insulation?
it means that signals from the pacemaker(in the atria) can only reach the ventricles through the AV node
what accounts for the difference in wall size in the cardiac chambers?
the amount of work that they do- more work, thicker wall
trace blood flow from the left atrium to the SA node?
the artery to the SA node comes from the right coronary artery
why are cells of the SA node autorhthmic?
spontaneous depolarization- the cell membrane allows sodium to leak into the cell which slowly raises its membrane potential to threshold
what accounts for the refractory period in cardiac muscle cells?
- the slow influx of calcium right after depolarization counters the repolarization of the potassium outflow
- this means that it takes longer to get back to the resting membrane potential
what is vagal tone?
constant parsay mpathetic stimulation (by the vagus nerve) that slows the pacemaker rate
what is an arrhytmia?
anything other than normal sinus rhythm
what is the difference between premature beats occurring in the atrium or the ventricle?
- PACs have normal QRS
- PVCs have wide, bizarre QRS
where is the location of the problem in heart blocks?
what is the ejection fraction?
the amount of blood ejected by a cardiac contraction compared to the amount of blood in the ventricle at the end of diastole
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