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15 Cards in this Set

  • Front
  • Back
What is the Q-T interval?
Contraction of the ventricles lasts almost from the beginning of the Q wave and continues to the end of the T wave. It normally lasts about 0.35 seconds.
What happens to the SA and AV node during sympathetic stimulation?
The permeability of the SA and AV node increases. The permeability of cardiac muscle to calcium increases resulting in an increased contractile strength.
Which cardiac structures generally have the slowest rate of cardiac action potential?
The A-V bundle myofibrils have a slow rate of conduction b/c they are considerably smaller than the normal atrial and ventricular muscles. There is also a diminished number of gap junctions between successive muscle cells in the conducting pathway.
What is Stokes-Adams syndrome?
A sudden onset of A-V block that comes and goes. Example would be an individual that has 75 P waves/min, atria are conducting normally. However, the A-V block that occurs allows only 35 QRS waves/min.
What is ejection fraction?
It is the stroke volume divided by the end-diastolic volume.
What is the ejection phase?
The aortic valve opens and blood flows into the aorta.
If the S-A node discharges at 00.0 sec, when will the action potential arrive at the epicardial surface at the base of the left ventricle?
After the S-A node discharges, the action potential travels thru the atria, thru the atrioventricular bundle system and finally to the vent. septum and throughout the ventricle. The last site it arrives at is at the base of the left ventricle which requires a transit time of 0.22 second.
What is first degree AV block?
This occurs when the P-R interval exceeds a value of 0.20 sec but without any dropprd QRS waves. During 2nd or 3rd degree block, QRS waves are dropped.
What is isovolumic contraction?
The pressure inside the left ventricle increases until the ventricular pressure is greater than the pressure in the aorta.
If the S-A node discharges at 0.00 sec, when will the action potential normally arrive at the A-V bundle of His?
It arrives at the A-V bundle at 0.12 sec. It arrives at the A-V node at 0.03 sec, and is delayed 0.09 sec in the A-V node, which results in an arrival time at the Bundle of His of 0.12 sec.
What does Einthovens law state?
It states that the voltage in lead 1 plus the voltage in lead 111, is equal in voltage to lead 11.
What is characteristic of atrial flutter?
It is typical to see several P waves for each QRS complex. One might also see 2 P waves/QRS, and others with 3 P waves/QRS complex. There is a rapid heart rate with irregular R-R intervals.
What is the general ventricular heart rate with atrial flutter?
App 120 bpm.
What occurs if the calcium ion concentration surrounding the cardiac myofibrils increases excessively?
The heart can go into spastic contraction. Excess of potassium conc in ECF causes the heart to become dilated b/c of the decrease in resting membrane potential of the cardiac muscle fibers.
What would be the result of an increase in sodium and calcium permeability at the S-A node?
An increase in heart rate. Increased K+ permeability causes hyperpolarization of the S-A node, which would result in a decrease in heart rate.