Review Sheet Excercise 31: Conduction System of the Heart and Electrocardiography

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The intrinsic Conduction System
1. List the elements of the intrinsic conduction system in order starting from the SA Node. SA node, AV Node, Av Bundle, left and right bundle branches, Purkinge fibers At what structure in the transmission sequence is the impulse delayed? Av Node

Allows completion of atrial contraction before initiation of ventricular systole. 2. Even though cardiac muscle has an inherent ability to beat. the nodal system plays a critical role in heart physiology. What is that role? Ensures that depolarization proceeds in an orderly manner from atria to ventricles ; accelerates and coordinates heart activity to effectively pump blood. Electrocardiography

3. Define ECG.
Recording of electrical changes occurring during heart activity 4.Draw an ECG wave form representing one heartbeat. Label the P,QRS, and T wavws: P-R interval; the S-T segment, and the Q-T interval.

5. Why does heart rate increase during running?
Exercise raises heart rate by acting through the sympathetic nervous system. Sympathetic nerve fibers release norepinephrine on the heart and the pace maker fires more rapidly. 6.Describe what happens in the cardiac cycle in the following situations. 1. ... the heart is in relaxation (diastole)

2. ... depolarization of the arteries
3. ... contraction of the aria
4. ... depolarization of the ventricles
5. ... contraction of the ventricles
6. ... repolarization of the ventricles
7. Define the following terms
1. tachycardia: Heart rate over 100 beats/minute
2. bradycardia: Heart rate below 60 beats/minute
3. fibrillation: Very rapid uncoordinated myocardial activity 8. Which would be more serious, atrial or ventricular fibrillation? Ventricular fibrillation.
The ventricles have major responsibility for ejecting blood from the heart 9. Abnormalities of the heart valves can be detected more accurately by auscultation than by electrocardiography. Why is this so? Most often serious valve problems can be...
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