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17 Cards in this Set
- Front
- Back
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the P wave
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is caused by electrical potentials generated when the atria depolarize before the contraction
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The QRS wave
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is caused by the potentials generated when the ventricles depolarize before contraction
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The T wave is
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caused by potentials generated as the ventricles recover from the state of depolarization. In ventricular muscle, 0.25 to 0.35 second after depolarization.
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No potential is recorded in the electrocardiogram when
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the ventricular muscle is either completely polarized or completely depolarized. Only when the muscle is partly polarized and partly depolarized does current flow from one part of the ventricles to another part
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The T wave in the normal electrocardiogram is a prolonged wave because
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the process of ventricular repolarization extends over a long period, about 0.15 second
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In the EKG - small line divisions upward or downward represent
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1 mV
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The time intervals between the dark lines on the EKG are
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0.20 seconds
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The time intervals with the fainter lines are
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0.04 seconds
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The time between the beginning of the P wave and the beginning of the QRS complex is the interval between the beginning of electrical excitation of the atria and the beginning of excitation of the ventricals. It is called the P-Q or P-R interval and is normally ___ second
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0.16 second
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Contraction of the ventricle lasts almost from the beginning of the Q wave (or R wave if Q absent) to the end of the T wave. This is called the Q-T interval and is about ___ second
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0.35 second
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Heart Rate counting the heavy lines:
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300, 150, 100, 75, 60, 50, 42ish
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standard bipolar limb leads
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Lead 1: neg on R arm, + on L arm
Lead 2: Neg on R arm, + on L leg Lead 3: neg on L arm + on L leg So both + on leg Both - on right arm |
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Einthoven's Law
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The sum of the voltages in leads I and III equals the voltage in lead II
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Chest leads (precordial leads)
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One electrode placed on the anterior surface of the chest directly over the heart and is the + electrode. The negative electrode called the indifferent electrode, is connected to the R arm, L arm and L leg all at the same time. Usually 6 standard chest leads are recorded, one at a time, from the anterior chest wall. The different recordings are known as V1, V2, V3, V4, V5 and V6
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In leads V1 and V2, the QRS recordings of the normal heart are
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mainly negative because the chest electrode is nearer to the base of the heart than to the apex
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The QRS complexes in leads V4, V5 and V6 are
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mainly positive because the chest electrode in these leads is nearer the heart apex which is the direction of electropositivity during most of depolarization
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Augmented unipolar limb lead
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2 of the limbs are connected through electrical resistance to the neg terminal of the electrocardiograph, and 3rd limb is connected to the + terminal. When + terminal is on R arm, the lead is known as the aVR lead. When on the L arm, the aVL lead. When on the L leg, the aVF lead. (remember the aVR lead is inverted)
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