ECG Lab Notes
ECG Lab Notes 272-01LL
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This 2 page Class Notes was uploaded by Juliana Bernard on Wednesday March 11, 2015. The Class Notes belongs to 272-01LL at University of Massachusetts taught by Dr. Gordon in Spring2015. Since its upload, it has received 155 views. For similar materials see Anatomy and Physiology II Lab in Kinesiology at University of Massachusetts.
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Date Created: 03/11/15
Lab Week 39313 Lab 7 Notes Electrocardiography SA node is a bundle of tissue in the heart with an unstable resting membrane potential because of this it has the ability to depolarize sending information to the AV node and onto the muscular components in the atria fthe SA node depolarizes it will result in an action potential and a threshold stimulus to the AV node It will also result in a depolarization an action potential and a release of chemical to the surrounding atrial muscle which will then result in the process of contraction quot describes beginning phase of cardiac cycle atrial contraction and ejection AV now receives threshold stimulus to reach it39s depolarization When the AV node depolarizes it achieves an action potential and will then cause a threshold stimulus to be send to the bundle of His Bundle of His now receives threshold stimulus and depolarizes When bundle of His depolarizes it achieves an action potential and sends threshold stimulus into bundle branches Bunde branches receive threshold stimulus depolarize and send their threshold stimulus onto the perkinje fbers which delve into the ventricular wall muscles Once perkinje fibers receive threshold stimulus they will depolarize and send an action potential and the relesase of chemical that will result in the contraction of the ventricles The depolarization and action potential in the SA node and atrial tissue happens at a different time than the depolarization and action potential in the ventricular tissue thus resulting in 2 differently timed contractions ECGs measure the depolarization and the repolarization that takes place throughout the heart during one cardiac cycle They do not show us actual contractions but they do show us the electrical events that occur and we know that if as certain electrical events occur we can infer that certain mechanical events have occurred for ex If we can see that the depolarization of the atria took place we can infer that the atria then contracted for ex If we can see that the ventricles have undergone depolarization we can infer that the ventricle will then eventually contract Depoarization usually takes place in a certain direction Depoarization and action potential follow a straight vector like movement In the ventricles typically move inside to outside To measure depolarization we use electrodes on each shoulder and each hip bone These measure electric current traveling towards or away from them Each ECG picture could oo different based on which direction you are collecting from ECGs are printed on graph paper time on the xaxis amplitude strength of AP on the yaxis Time on the xaxis One small box 04 seconds One large block 2 seconds Ampitude strength of action potential on the yaxis One small box 1 mm 1 mV One large block 5 mm 5 mV soeectric line no electricity space electricity isn39t changing time between transitions from de to re polarization PWave The depolarization of the atria First half of the pwave is the depolarization of the right atria second half is of the left atria Seeing a pwave indicates that depolarization of the atrial tissue has occurred We can infer that contraction of the atria has also occurred when we see a pwave There is then a space after the pwave on the isoelectric line where information from the SA node to the AV node and further on QRS Complex The depolarization of the ventricle The Q wave the first downward deflection being seen before an R wave Represents the depolarization of the septum sn39t always seen because it is not a big bundle of tissue If you do see a large Q wave it is a bad sign it is a sign of a heart attack The R wave the upward spike between Q and S waves Represents the depolarization of the right ventricle The 8 wave the first downward deflection after an R wave Represents the depolarization of the left ventricle TWave The repolarization of the ventricle setting them up for another electrical event Also need to be able to identify certain segments and intervals lnterval wave isoelectric line PR interval goes from beginning of pwave to the start of the next wave R or Q if present mportant component of understanding if information is going through the AV node Segment no waves section between two waves ST segment After swave and before twave no wave Another indicative component of myocardial infarction
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