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Antegrade Impulse
an impulse that travels through the conduction system in the correct direction
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Retrograde Impulse
an impulse that travels through the conduction system in the reverse direction
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Ectopy
a broad term indicating any kind of abnormal impulse
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Hyperkalemia
As potassium levels rise (normal 3.5-5.0 mEq/L) T-waves become higher and more peaked
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Anastomosis
communication between two or more vessels
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Poiseulle's Law
a low of physiology stating that blood flow through a vessel is directly proportional to the radius of the vessel to the 4th power
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Cardiac Cycle
the period of time from the end of one cardiac contraction to the end of the next
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Diastole
Rest - the period of time when the myocardium is relaxed and cardiac filling and coronary perfusion occur
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Systole
Contraction - the period of the cardiac cycle whrn the myocardium is contracting
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Ejection Fraction
ratio of blood pumped from the ventricle to the amount remaining at the end of diastole
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Stroke Volume
the amount of blood ejected by the heart in one cardiac contraction
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Preload
the pressure within the ventricles at the end of diastole, commonly called the end-diastolic volume
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Starling's Law of the Heart
law of physiology stating that the more the myocardium is stretched, up to a certain amount, the more forceful the subsequent contraction will be
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Afterload
the resitance against which the heart must pump
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Factors Affecting Stroke Volume
Preload Cardiac Contractility Afterload
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Cardiac Output
the amount of blood pumped by the heart in 1 minute (Stroke Volume x heart rate = Cardiac Output)
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Chronotropy
pertaining to heart rate
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Inotropy
pertaining to cardiac contractile force (Strength)
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Dromotropy
pertaining to the speed of impulse transmission (Electrical Conductivity)
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Intercolated Discs
specialized bands of tissue inserted betwen myocardial cells that increase the rate in which the action potential is spread from cell to cell
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Syncytium
group of cardiac muscle cells that physilogically function as a unit
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Electrolytes that effect cardiac function
- Sodium (Na+)-Major role in depolarizing the myocardium,
- Calcium (Ca++) takes part in myocardial depolarization and myocardial contraction
- Potassium (K+) influences repolarization
- Chloride (Cl-)
- Magnesium (Mg++)
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Hypercalcemia
- increase in serum calcium
- increased myocardial contractility
- shortens repolarization
- ST segment shortens (sometimes T-wave looks as if it's on QRS)
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Hypocalcemia
decrease in serum calcium, decreased myocardial contractility and increased electrical irratibility, prolongs repolarization, prolongs ST segment
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Hyperkalemia
increase in Potassium, decreases automaticity and conduction
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Hypokalemia
decrease in Potassium, increases irritability
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Repolarization
return of a muscle cell to its preexcitation resting state
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Excitability
the ability to be simulated to contract, respond to electrical stimulus
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Conductivity
the ability to transmit(propagate) an electrical impulse from one cell to the another
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Automaticity
pacemaker cells capability to self-depolarize, the ability to selfgenerate an impulse
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COntractility
the ability of the muscle fibers to contract, shortening of the muscle fibers (mechanical property)
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Internodal Atrial Pathways
Connect the SA node to the AV node
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artifact
deflection on the ECG produced by factors other than the hearts electrical activity, such as muscle tremors, shivering, patient movement, loose electrodes, 60 hertz interference, machine malfuntion
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Bipolar Limb Leads
ECG leads applied to the arms and legs that contain 2 electrodes of opposite (+ & -) polarity. Leads I, II and III
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Einthoven's Triangle
the triangle around the heart formed by the bipolar limb leads
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