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103 Cards in this Set
- Front
- Back
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Starling's law of the heart
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The more the myocardium is stretched (up to a certain point) the more forceful the subsequent contraction will be.
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resting membrane potential
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The electrical charge difference inside a cell membrane measured relative to just outside the cell membrane.
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threshold potential
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The value of the membrane potential at which an action potential is produced as a result of depolarization in response to a stimulus.
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refractory period
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The period after effective stimulation during which excitable tissue fails to respond to a stimulus of threshold intensity.
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premature atrial complex
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A cardiac dysrhythmia characterized by an atrial beat occurring before the expected excitation and indicated on the electrocardiogram as an early P wave.
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premature junctional contraction
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A cardiac dysrhythmia that occurs during sinus rhythm earlier than the next expected sinus beat and is caused by premature discharge of an ectopic focus in the atrioventricular junctional tissue.
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premature ventricular complex
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A cardiac dysrhythmia characterized by a ventricular beat preceding the expected electrical impulse and indicated on the electrocardiogram as an early, wide QRS complex without a preceding related P wave.
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ventricular tachycardia
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A tachycardia that usually originates in the Purkinje fibers.
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paroxysmal supraventricular tachycardia
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An ectopic rhythm in excess of 100 beats per minute and usually faster than 170 beats per minute that begins abruptly with a premature atrial of junctional beat and is suported by an atrioventricular nodal reentry mechanism or by an atrioventricular reentry involving an accessory pathway.
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apex
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The lower heart border.
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point of maximal impulse (PMI)
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The physical examination landmark that is an indicator of the heart's position within the thorax.
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fibrous pericardium
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The outer, tough, inelastic sac.
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serous pericardium
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The inner, thin, two-layered, fluid-secreting membrane.
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epicardium
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The visceral layer of the serous pericardium.
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myocardium
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The thick, middle, muscular layer that makes up the bulk of the heart wall.
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endocardium
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The smooth, thin layer of tissue that lines the heart chambers and valves.
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systemic circuit
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A large circuit; involves the left side of the heart and vessels, which carry blood to the body and back to the right heart.
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pulmonary circuit
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A small circuit; includes the right side of the heart and vessels, which carry blood to the lungs and back to the heart.
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interatrial septum
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The wall that divides the two upper chambers.
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interventricular septum
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The thicker wall that divides the two lower chambers.
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tricuspid valve
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Separates the right atrium from the right ventricle.
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pulmonic valve
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Separates the right ventricle from the pulmonary arteries.
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mitral valve
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Separates the left atrium from the left ventricle.
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aortic valve
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Separates the left ventricle from the aorta.
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atrioventricular (AV) valves
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The tricuspid and mitral valves.
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chordae tendineae
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Thin strands of fibrous cords ("heart strings").
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semilunar valves
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The aortic and pulmonic valves.
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collateral vessels/ collateral circulation
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Small arteries that interconnect the right and left coronary artery branches.
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sympathetic nervous system
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Prepares the body to function under stress.
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parasympathetic nervous system
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Regulates the calmer functions.
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myocardial cells
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Working or mechanical cells.
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actin and myosin
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Contractile protein filaments.
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electrolyte
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A substance whose molecules dissociate into charged particles (ions) when placed in water, producing positively and negatively charges ions.
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cation
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An ion with a positive charge.
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anion
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An ion with a negative charge.
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membrane channels (pores)
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Openings through which ions pass back and forth between the extracellular and intracellular spaces.
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concentration gradient
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Particles in a solution move from areas of higher concentration to areas of lower concentration.
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electrical gradient
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Like charges repel; opposite charges attract.
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sodium-potassium pump
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A mechanism that actively transports ions across the cell membrane against its electrochemical gradient.
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right bundle branch
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Conducts the electrical impulse to the right ventricle.
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left bundle branch
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Divides into two divisions: the anterior fascicle and the posterior fascicle.
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anterior fascicle
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Carries the electrical impulse to the anterior wall of the left ventricle.
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posterior fascicle
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Carries the electrical impulse to the posterior wall of the left ventricle.
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Purkinje fibers
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Conduction fibers.
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His-Purkinje system
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The bundle of His, bundle branches, and Purkinje fibers.
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P wave
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Depicts atrial depolarization, or the spread of the impulse from the SA node throughout the atria.
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PR interval
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Represents the time from the onset of atrial depolarization to the onset of ventricular depolarization.
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PR segment
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The short isoelectric line from the end of the P wave to the beginning of the QRS complex.
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QRS complex
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Depicts ventricular depolarization, or the spread of the impulse throughout the ventricles.
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ST segment
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Represents the end of ventricular depolarization and the beginning of ventricular repolarization.
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T wave
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Represents the latter phase of ventricular repolarization.
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U wave
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Is thought to represent further repolarization of the ventricles.
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QT interval
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Represents both ventricular depolarization and repolarization.
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R-R interval
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From one R wave to the next R wave.
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biphasic deflection
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A deflection having both a positive and negative component.
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absolute refractory period
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During this period the cells absolutely can't respond to a stimulus.
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relative refractory period/ vulnerable period of repolarization
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During this perios the cardiac cells have repolarized sufficiently to respond to a strong stimulus.
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supernormal period
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During this period the cardiac cells will respond to a weaker than normal stimulus
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The heart has three tissue layers. What are they?
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1. Endocardium
2. Myocardium 3. Pericardium a. Visceral pericardium (epicardium) b. Parietal pericardium |
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What are the 4 chambers?
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Right atrium, right venticle, left atrium, left ventricle.
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Two semilunar valves:
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Pulmonary valve- between the right ventricle and the pulmonary trunk
Aortic valve- between the left ventricle and the aorta |
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Two atrioventricular valves:
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Tricuspid valve- between the right atrium and ventricle
Mitral valve- between the left atrium and ventricle |
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aorta
pulmonary circulation vena cava left ventricle systemic circulation right atrium left atrium righ ventricle |
vena cava, right atrium, right ventricle, pulmonary circulation, left atrium, left ventricle, aorta, systemic circulation
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How does the heart receive its nutrients from the blood? Is it during systole or diastole?
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Blood drains into the coronary arteries during diastole.
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What are the three layers of the wall of an artery?
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Tunica intima, tunica media, tunica adventia.
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cardiac cycle
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From the end of one contraction to the next.
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diastole
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When the myocardium is relaxed and cardiac filling and coronary perfusion occurs.
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systole
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When the myocardium is contracting.
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ejection fraction (What is normal?)
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Ratio of the amount of blood pumped from the ventricles to the amount remaining at the end of diastole.
(2/3 is the normal ejection fraction) |
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stroke volume
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The amount of blood ejected by the heart in one contraction.
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cardiac output
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The volume of blood the heart pumps in 1 minute.
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preload
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The pressure within the ventricles at the end of diastole; commonly called the end-diastolic volume.
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afterload
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The resistance against which the heart must pump.
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cardiac output = stroke volume x
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heart rate
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cardiac output x systemic vascular resistance =
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blood pressure
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What 2 components of the autonomic nervous system regulate the heart?
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Parasympathetic system, sympathetic system.
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Sympathetic system neurotransmitter?
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Norepinephrine.
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2 principal types of sympathetic system receptors?
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Alpha and beta.
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Where are the alpha receptors located? What do they cause?
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In the peripheral vessels; vasoconstriction.
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There are 2 types of beta receptors- beta 1 and beta 2. Where are they located? What do they cause?
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Beta 1 receptors in the heart cause an increase in rate and contractility.
Beta 2 receptors in the lungs cause bronchodilation. |
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Parasysmpathetic system neurotransmitter?
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Acetylcholine.
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In the heart, parasympathetic system controlled by the _____ nerve?
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vagus
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chronotropy
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Pertaining to heart rate.
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inotropy
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Pertaining to cardiac contractile force.
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dromotropy
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Pertaining to the speed of impulse transmission.
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What are the 3 electrolytes that most affect cardiac function?
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Na+
K+ Ca++ |
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intercalated discs
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Specialized bands of tissue inserted between the myocardial cells that increase the rate at which the action potential is spread from cell to cell.
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syncytium
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A group of cardiac muscle cells that physiologically function as a unit.
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The heart has 2 syncytia...
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Atrial syncytium, ventricular syncytium.
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The only way the impulse can be conducted is through the ________________ node.
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atrioventricular
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resting potential
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The normal resting state of cardiac cells.
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cardiac depolarization
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Quick reversal of the resting potential caused by a rapid influx of Na+ into the cell.
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action potential
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An influx of positive ions into the cell followed by a change of polarity.
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repolarization
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Return of a muscle cell to its preexcitation resting state.
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excitability
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The ability of the cells to respond to an impulse.
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automaticity
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The ability of a cell to spontaneously generate and discharge an impulse.
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conductivity
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The ability of a cell to transmit an impulse.
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contractility
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The ability of the cell to shorten and lengthen muscle fibers.
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pacemaker cells
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Cells that spontaneously depolarize.
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normal P wave
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Upright, slightly rounded, smooth.
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normal PR interval
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0.12-0.20 seconds (3-5 small boxes).
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normal QRS
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Less than 0.12 seconds (less than 3 boxes).
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normal T wave
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Rounded and upright, usually taller and wider than the P wave.
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