Lab 3: Exercise 45 & 46
Lab 3: Exercise 45 & 46 KNES 2169L
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This 0 page Class Notes was uploaded by Shanavia Bates on Sunday February 7, 2016. The Class Notes belongs to KNES 2169L at University of North Carolina - Charlotte taught by in Spring 2016. Since its upload, it has received 66 views. For similar materials see Anatomy and Physiology II Lab in Kinesiology at University of North Carolina - Charlotte.
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Date Created: 02/07/16
KNES 2169L Lab 3 Electrocardiogram and Heart Sounds Figure 452 gt SA Sinoatrial gt AV atrioventricular What causes 0 Sl Closing of the AV valves louder and longer than SZ lub rst heart sound quotT and M valves snap shutquot and P and A valves opens up o 52 Closing of semilunar valves dubsecond heart sound quotP and A valves snap shutquot and T and M opens up 0 S3 lling out the ventricles o Murmurs Abnormal sounds signify improper sound of waves Gap junction it39s in all cardiac cells Allow action potentials to pass from one cell to the next depolarization Functional syncytium cells of heart are functionally in sync with each other Components of the heart39s conduction system A NODE To INTERATRIAL PATHWAYS T0 AV NODE T0 AV BUNDLE T0 BUNDLE BRANCHES T0 PURKINJE FIBERS lt distributes the Aps throughout the myocardium a slight delay occurs as the impulse passes through the AV node insuring sequential rather than simultaneous excitationcontraction of the atrial and ventricular syncytia The delay is important AV node because the atrium have a chance to relax The SA node is called the pacemaker of the heart because it depolarizes at a faster rate than other areas of the conduction system can39t The electrocardiogram is a graphical record of the electrical activity of the heart that is depolarization and repolarization of the atria and ventricles A skilled interpreter can obtain much information from this relatively simple noninvasive diagnostic tool but keep in mind that the ECG is but one tool which must be combined with others in real clinical situation Principles of an ECG 0 An ECG is a report of the potential difference between large masses of cells in one region relative to another in the heart The ECG begins at zero because ALL myocardial cells shave the same potential at rest All are polarized They are all the SAME As the SA node begins its spontaneous depolarization the surrounding myocardial cells in the upper part of both atria receive the impulses also When these upper atrial cell depolarize that makes them DIFFERENT from the lower atrial cells which for the moment remain in a polarized state A potential difference exists and when this difference is at its greatest magnitude the P wave is at its greatest height Once ALL atrial cells attain the depolarized state simultaneously there is NO difference between the upper atrial cells and lower atrial cells and the P wave returns to zero Repolarization of the atrial masses would produce a second a separate peak but as you have by now established it is masked or hidden by the much larger event VENTRICULAR DEPOLARIZATION The same process which occurs in the atria occurs after a short delay of conduction through the AV node in the ventricles The ECG at zero means that all ventricular cells are the SAME polarized As SOME ventricular cells receive the AP rst and become depolarized the difference between these ventricular cells and other ventricular cells still polarized is detected by our surface electrodes and the peak of the R wave is reached Once all the ventricular cells depolarize zero is regained Finally the T wave is produced as the potential difference is detected when SOME ventricular cells have REPOLARIZED and the rest are momentarily still in the DEPOLARIZED state Again zero is regained when ALL ventricular cells attain the same state of REPOLARIZATION Wave forms O 0000 O O Atrial depolarization P wave atrial contraction Atrial repolarization TA wave covered by QRS atrial relaxation Ventricular depolarization QRS wave ventricular contraction Ventricular repolarization T wave ventricular relaxation Time for cardiac impulse from SA node through AV node PQ interval atria contract and relax Ventricle depolarize ST segment time for ventricles to contract Time for ventricular depolarization to end of ventricular repolarization QT interval ventricles contract and relax Major Cardiac Arrhythmias O O O Bradycardia heart rate less than 60 beatsminutes Athletes bradycardia slower heart rate is endurance trained athletes Result of higher levels of parasympathetic inhibition of the SA node Tachycardia heart rate faster than 100 beatsminute when person is at rest Ventricular tachycardia abnormally fast ectopic pacemakers in ventricles cause them to beat rapidly and independent of atria Flutter contraction rapid 200300 beatsminute but coordinated 0 AV Block rst degree PR interval is greater than 20 seconds AV Block second degree AV node damaged so only 2 34 waves can pass P waves without QRS AV Block third degree complete heart block No waves can pass P waves dissociated from QRS Electrical De brillation to stop brillation electric shock given to chest Depolarizes all myocardial cells at the same time Sinus Rhythm pace or rhythm set by the SA node Ectopic Foci cells located outside of SA node that assume pacemaker function when SA node is not functioning
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