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33 Cards in this Set
- Front
- Back
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p-wave
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atrial depolarization
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pr interval
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time from onset of atrial activation to ventricular activation
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qrs complex
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ventricular depolarization
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t wave
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ventricular repolarization
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sa node
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(sinoatrial node)
the pacemaker |
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av node
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atrioventricular node
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order of electrical impulses in the heart
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SA node, AV node, bundle of His, bundle branches, Purkinje fibers
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myocardial metaboism
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-cardiac muscle depends on constant ATP production
-ATP made in mitochondria -if myocardial tissue is not adequately perfused, anaerobic metabolism becomes a source of energy -energy is needed for contraction, electrical excitiation, membrane transport and synthesis |
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normal intracardial pressure
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table 29-1
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myocardial oxygen consumption
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determined by 3 factors:
1-wall stress during systole (estimated by bp) 2-druation of systolic wall tension 3-contractile state of myocardium *Oxygen delivered by the coronary arteries |
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coronary arteries
LCA |
divides into left andterior descending (LCA)and circumflex artery
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coronary arteries
LAD |
supplies left and right ventricle adn interventricular septum, often branches to posterior surface of left atrium and left ventricle
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coronary arteries
circumflex |
supplies left atrium and lateral wall of left ventricle
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coronary arteries
RCA |
divides into conus, right marginal branch and posterior descending
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coronary arteries
conus |
supplies upper right ventricle
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coronary arteries
right marginal |
supplies apex
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coronary arteries
posterior descending |
supplies smaller branches to both ventricles
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factors directly affecting cardiac performance
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preload, afterload, heart rate, contractility.
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preload
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pressure generated in left ventricle at the end of diastole.
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afterload
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resistance or impedance to ejection of blood from left ventricle, aortic systemic pressure used as an index
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heart rate
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characteristic of cardiac tissue, subject ot nerual and hormonal influence
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contractility
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characteristic of cardiac tissue, subject to nerual and hormonal influence
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Frank-Starling law of the heart
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.length-tension relationship of cardiac muscle
.relates resting sarcomere length to tension generated .volume of blood at the end of diastole is directly related to force of contraction during next systole .preload (filling pressure) used as an index of ventricular volume |
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laplace's law
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wall tension directly related to product of intraventricular wall to produce a given pressure depends on ventricular size
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sympathetic activity
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-sympathetic fibers innervate atria and ventricles
-sympathetic activity enhances myocardial performance and increases HR -norepinepherine binds beta-adrenergic receptors on cardiac cells to increase intracellular Ca2+, which inceases contractile strength of heart muscle. |
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parasympathetic activity
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-parasympathetic fibers from the vagus innervate atria, ventricles, and SA and AV notes
-vagus nerve releases acetylcholine -parasympathetic activity decreases HR -strong vagal stiumlation can block cardiac action potentials transmitted through the atria |
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neural reflexes:
bainbridge reflex |
causes HR to increase after IV infusions of blood/fluids
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neural reflexes:
baroreceptor reflex |
if bp is low, reflex increases HR and causes vasoconstriction to increase BP
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stroke volume
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-volume of blood ejected with each heart beat
-depends on force of contraction -force of contraction depends on myocardial contractility (degree of myocardial fiber shortening) |
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force of contraction
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determined by:
1-changes in ventricular stretch caused by changes in ventricular volume (preload) 2-sympathetic activation of ventrical *inotropic agents affect contractility |
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inotropic agents
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postiive: increase the velocity of contraction and SV, include TH, epinepherine, norepinephrine, dopamine, and isoproterenol
negative: decreased velocity of contraction adn SV; include alcohol, procainamide, quinidine and propanolol |
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cardiac output (CO)
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quantity of blood pumped by left ventricle into the aorta each minute
CO=HRxSV =normally about 5 L/min |
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ejection fraction
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-not all of the blood is ejected from the ventricle
-normal ejection fraction is about 60-75% |
