EKG review sheet

EKG review sheet - Chap 1 EKG stands for Electrocardiogram,...

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Chap 1 EKG stands for Electrocardiogram, and records heart’s electrical activity. When resting cardiac cells are electrically polarized, maintained by membrane pumps. Cardiac cells loose negativity thru depolarization fundamental electrical event of the heart, flow of electricity across heart, detected by electrodes Repolarization is restoring polarity Pacemaker Cells - electrical power house of cell, 5-10µm, no true resting potential, dominant ones in right atrium. Called Sinoatrial (SA) node and fire 60-100 times a minute, vagal will slow it down and sympathetic speeds it up. Not seen on EKG Electrical conducting cells - hard wiring of heart, long and thin, carry current fast and efficiently to distant regions of heart. Bachmans bundle rapid activation of left atrium from right Myocardial Cells - contractile machinery of heart, contract and relax which delivery blood to the body. 50-90µm, contain actin and myosin Excitatory Contraction Coupling- when myocardial cell gets Ca2+ it contracts, less efficient at transmitting electric signals. Seen on EKG Action Potential – one cycle of depolarization and repolarization Duration in fraction of second, Amplitude in milivolts, Configuration refers to shape. Small Square – 0.04 seconds Big square - 0.2 seconds Atrial Depolarization- Sinus Node fires spontaneously, not visible on EKG, wave of depolarization spreads out, and when myocardial cells depolarize there’s an atrial contractions, electrode placed on body can records burst of electrical activity (p-wave) . SA node in right atrium right atrium depolarizes before left atrium. First half of p wave is right atrial depolarization and second half is left atrial depolarization. Electrical Gate at junction between atria and ventricles, current must be funneled thru interventricular septum, which separates right and left ventricles, Atrioventricular node (AV) slows conduction, (slowed by vagal and sped up by sympathetic) pause lasts fraction of a second so atria finish contracting before ventricles being contracting. Ventricular Depolarization- has electrical conducting cells made of 3 parts Bundle of His- from AV node and splits into right and left bundle branches , the right bundle brings current to right side of interventricular septum, to apex of the right ventricle. The left bundle branch divides into Septal Fascicle which depolarizes interventricular septum and the Anterior Fascicle runs along anterior surface of left ventricle and the Posterior Fascicle sweeps over posterior surface of left ventricle. The right and left bundle branches turn into Terminal Purkinje Fibers which deliver electrical current into ventricular myocardium
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Ventricular Depolarization shown by QRS complex first deflection down is Q wave , first upward deflection is R wave ,(if second upward deflection R ‘ wave ) and if downward deflection followed by upward deflection it is an S wave. T wave is ventricular repolarization which can be seen on EKG. PR interval
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EKG review sheet - Chap 1 EKG stands for Electrocardiogram,...

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