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92 Cards in this Set
- Front
- Back
SA node is located in
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superior right atrium
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What created heart beat
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SA nodal pacemaker potential
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AP's from SA node are propagated to right atrium AV node by
left atrium by |
INTERNODAL TRACTS
BACHMANS BUNDLE |
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AV node is located
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inferior right atrium
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What is the function of AV node
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Delays signal to allow atria to beat first and help fill ventricles
Also a back up pacemaker |
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Overdrive suppression
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signal from SA node suppresses AV nodal pacemaker
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Ventricular conduction system
starts with |
bundle of His and branches into righ and left bundle branches which give rise to smaller branches
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What controls heart rate
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ANS
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Sympathetic innervation... heart rate via...
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increases
beta 1 receptors |
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Parasympathetic innervation decreases heart rate via
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muscarinic receptors
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Main 2nd messenger in heart
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cAMP
cAMP dependent protein kinase phosphorylates "funny" Na channel increasing its rate of opening beta 1 receptors stimulate cAMP via Gs M2 receptors inhibit cAMP via Gi |
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Sinus rhythm
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Normal
set by SA node, adult at rest is 70-80 bpm |
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Abnormal rhythms
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AV nodal - starts if SA node fails since overdrive suppression stops - 40-50 beats per min
Ventricular - from ventricular conduction system if both nodes fail 20-40 bpm Ectopic- in hypoxia, when heart cells become depolarized |
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Purkinje cells are specialized for
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high velocity conduction, not contraction
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Phase 0
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Stimulus opens voltage gated Na channels (Na rushes in), membrane rapidly depolarizes
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Phase 1
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Na gates close quickly, K gates open
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Plateau phase
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200-250 msec, sustains contraction
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Phase 2
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slow Ca channels open, Ca binds to Ca channels on SR, releases Ca into cytosol which leads to contraction
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Phase3
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Repolarization - Ca channels close, K channels remain open
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Phase 4
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Resting membrane potential
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Standard leads=
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Einthovens leads
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Augmented leads =
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Goldbergers leads
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What causes P wave
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phase 0 in atrium
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What causes Q, R, S wave
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phase 0 in ventricle
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What causes T wave
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phase 3 in ventricle
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What do intervals represent
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Delay in propagation
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P-R interval is
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AV node delay
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QRS (Q-S) interval
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ventricular conduction delay
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Q-T interval
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Duration of ventricular action potential
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Segments vs Intervals
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Segments are straight or continuously curved lines between events
Intervals are periods of time that include events |
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Stroke VOlume SV is
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amount of blood the heart forces in aorta with every heart beat
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End diastolic volume
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amount of blood in heart just before contraction
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End systolic volume
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amount of blood remaining in heart just after contraction
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Formula for SV
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SV = EDV - ESV
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How can you increase SV
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Increase EDV or decrease ESV
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Cardiac output formula
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CO= SV * HR= (EDV-ESV) * HR
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What is the most important measure of cardiac performance
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Cardiac output
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Normal cardiac output
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4-6 L/min
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How do you increase CO
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Increase HR
Increase EDV Decrease ESV |
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Ejection fraction
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Fraction of EDV that was ejected
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Formula for EF
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SV/EDV
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Normal EF
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0.5-0.75
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What sets preload
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Ventricular filling pressure
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What regulates filling pressure
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CENTRAL VENOUS PRESSURE
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Best clinical measure of preload
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EDV
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Inotropic state is
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hearts contractility - both rate of contraction and total force
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Increasing inotropic state..
ESV |
decreases
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What determines inotropic state
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Ca
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Lusitropic state
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Rapidity at which heart relaxes
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Net effect of catecholamines
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Increase both inotropic and lusitropic states of heart and shorten systole while increasing contractility
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Afterload
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pressure against which ventricle ejects stroke volume
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Contraction velocity is ... to afterload
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inversely related
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Inotropic state is
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hearts contractility - both rate of contraction and total force
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P wave causes
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atrial contraction
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Increasing inotropic state..
ESV |
decreases
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QRS wave causes
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ventricular contraction
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What determines inotropic state
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Ca
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S1 first heart sound occurs when
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ventricular pressure > atrial pressure so AV valves close
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Lusitropic state
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Rapidity at which heart relaxes
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S2 second heart sound occurs when
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arterial pressure closes arterial valves
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Net effect of catecholamines
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Increase both inotropic and lusitropic states of heart and shorten systole while increasing contractility
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SP systolic pressure
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maximum arterial pressure
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Afterload
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pressure against which ventricle ejects stroke volume
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DP diastolic pressure
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minimum arterial pressure
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Contraction velocity is ... to afterload
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inversely related
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Pulse pressure
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SP-DP
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P wave causes
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atrial contraction
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A wave is caused by
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atrial contraction
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QRS wave causes
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ventricular contraction
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S1 first heart sound occurs when
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ventricular pressure > atrial pressure so AV valves close
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S2 second heart sound occurs when
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arterial pressure closes arterial valves
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SP systolic pressure
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maximum arterial pressure
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DP diastolic pressure
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minimum arterial pressure
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Pulse pressure
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SP-DP
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A wave is caused by
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atrial contraction
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Inotropic state is
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hearts contractility - both rate of contraction and total force
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Increasing inotropic state..
ESV |
decreases
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What determines inotropic state
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Ca
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Lusitropic state
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Rapidity at which heart relaxes
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Net effect of catecholamines
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Increase both inotropic and lusitropic states of heart and shorten systole while increasing contractility
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Afterload
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pressure against which ventricle ejects stroke volume
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Contraction velocity is ... to afterload
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inversely related
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P wave causes
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atrial contraction
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QRS wave causes
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ventricular contraction
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S1 first heart sound occurs when
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ventricular pressure > atrial pressure so AV valves close
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S2 second heart sound occurs when
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arterial pressure closes arterial valves
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SP systolic pressure
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maximum arterial pressure
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DP diastolic pressure
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minimum arterial pressure
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Pulse pressure
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SP-DP
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A wave is caused by
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atrial contraction
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c wave is when
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ventricular contraction pushes AV valves closed
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v wave is when
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blood returning from veins builds up behind AV valves
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