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Exercise 31 Conduction system of the heart and electrocardiography
Terms in this set (18)
At what structure in the transmission sequence is the impulse temporarily delayed? Why?
AV node, Allows completion of atrial contraction before initiation of ventricular systole
List the elements of the intrinsic conduction system in order, starting from the SA node
A) SA Node -> AV node -> AV Bundle -> left & right bundle branches -> purkinje fibers
B) SA Node -> AV node -> AV Bundle -> purkinje fibers -> left & right bundle branches
C) SA Node -> AV Bundle -> AV node -> left & right bundle branches -> purkinje fibers
At what structure in the transmission sequence is the impulse temporarily delayed?
The AV node because it allows completion of atrial contraction before initiation of ventricular systole.
Even though cardiac muscle has an inherent ability to beat, the nodal system plays a critical role in heart physiology. What is that role?
- Organization of depolarization, and coordinates heart activity
- Ensures that depolarization proceeds in an orderly manner from atria to ventricles. It also accelerates and coordinates heart activity.
Recording of electrical changes in heart activity
Why does the heart rate increase during running?
- Release of norepinephrine by the sympathetic nervous system
- Our muscles need more oxygen when running
Describe what happens in the cardiac cycle immediately before the P wave?
Heart is in relaxation (diastole)
Describe what happens in the cardiac cycle during the P wave?
Depolarization of the atria
Describe what happens in the cardiac cycle immediately after the P wave (P-R segment)
Contraction of the atria
Describe what happens in the cardiac cycle during the QRS wave/complex?
Depolarization of the ventricles
Describe what happens in the cardiac cycle immediately after the QRS wave/complex (S-T) interval?
Contraction of the ventricles
Describe what happens in the cardiac cycle during the T wave
Repolarization of the ventricles
Heart rate over 100 beats/min
Heart rate below 60 beats/min
Very rapid uncoordinated myocardial activity
Abnormalities of heart valves can be detected more accurately by auscultation than by electrocardiography. Why is this so?
Most often, serious valve problems can be detected (heard) with a stethoscope. However, since valves are not part of the depolarization pathway of the heart, their inefficiency would not be recorded on an ECG.
Given what you know about the correlation between the ECG waves and the electrical events in the heart, what wave of the ECG tracing would you expect to be affected in atrial fibrillation? Explain.
The P Wave should be affected since this wave is generated by atrial depolarization.
Which would be more serious, atrial or ventricular fibrillation and why?
Ventricular fibrillation, the ventricles bear major responsibility for pumping blood from the heart to the lungs and all other body organs.
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