Chapterg02:gBasicgElectrophysiologygAehler
t:gECGsgMadegEasy,g6thgEdition
MULTIPLEgCHOICE
1. Ingmostgpatients,gthegsinoatrialg(SA)gandgatrioventricularg(AV)gnodesgaregsuppliedgbygthe
coronarygartery.
a. right
b. leftgmain
c. circumflex
d. leftganteriorgdescending
ANS:g A
ThegSAgnodegreceivesgitsgbloodgsupplygfromgthegSAgnodegarterygthatgrunsglengthwisegthrough
gthegcentergofgthegnode.gThegSAgnodegarterygoriginatesgfromgthegrightgcoronarygarterygingabou
tg60%gofgpeople.gThegAVgnodegisgsuppliedgbygthegrightgcoronarygarteryging85%gtog90%gofgth
egpopulation.gIngthegremainder,gthegcircumflexgarterygprovidesgthegbloodgsupply.
OBJ:g Describegtheglocation,gfunction,gand,gwhengappropriate,gthegintrinsicgrategofgthegfollowinggstruct
ures:gsinoatrialgnode,gatrioventriculargbundle,gandgPurkinjegfibers.
2. Thegintrinsicgrategofgthegatrioventricularg(AV)gbundlegisg beats/min.
a. 20gtog40
b. 40gtog60
c. 60gtog80
d. 80gtog100
ANS:g B
ThegAVgbundleghasgpacemakergcellsgcapablegofgfiringgatgagrategofg40gtog60gbeats/min.
OBJ:g Describegtheglocation,gfunction,gand,gwhengappropriate,gthegintrinsicgrategofgthegfollowinggstruct
ures:gsinoatrialgnode,gatrioventriculargbundle,gandgPurkinjegfibers.
3. HowgdogyougdeterminegwhethergthegatrialgrhythmgongangECGgtracinggisgregulargorgirregular?
a. ComparegQTgintervals.
b. ComparegPRgintervals.
c. ComparegRgtogRgintervals.
d. ComparegPgtogPgintervals.
ANS:g D
Togevaluategthegregularitygofgthegatrialgrhythmgongagrhythmgstrip,gthegintervalgbetweengtwogcon
secutivegPgwavesgisgmeasured.gThegdistancegbetweengsucceedinggP-
Pgintervalsgisgmeasuredgandgcompared.gIfgthegatrialgrhythmgisgregular,gthegP-
Pgintervalsgwillgmeasuregthegsame.
OBJ:g g Describegagsystematicgapproachgtogtheganalysisgandginterpretationgofgcardiacgdysrhythmias.
4.
isgthegabilitygofgcardiacgpacemakergcellsgtogspontaneouslyginitiategangelectricalgimpuls
egwithoutgbeinggstimulatedgfromganothergsource,gsuchgasgagnerve.
a. Excitability
b. Conductivity
c. Automaticity
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d. Contractility
ANS:g C
Thegabilitygofgcardiacgpacemakergcellsgtogcreategangelectricalgimpulsegwithoutgbeinggstimulate
dgfromganothergsourcegisgcalledgautomaticity.gExcitabilitygisgthegheartgmuscles’gabilitygtogresp
ondgtogimpulsegorgstimulus.gConductivitygisgthegabilitygofgthegcardiacgcellsgtogreceivegandgtran
smitgangelectricalgimpulse.gContractilitygisgthegcontractiongofgthegheartgmusclegwhichgproduce
sgthegheartbeat.
OBJ:g g Describegthegprimarygcharacteristicsgofgcardiacgcells.
5. Ingthegheart’sgconductiongsystem,gtheg
receive(s)gangelectricalgimpulsegfromgthegbundl
egofgHisgandgrelay(s)gitgtogthegPurkinjegfibersgingthegventriculargmyocardium.
a. atrioventricularg(AV)gnode
b. atria
c. sinoatrialg(SA)gnode
d. rightgandgleftgbundlegbranches
ANS:g D
Thegrightgandgleftgbundlegbranchesgdividegintogsmallergandgsmallergbranchesgandgthengintogags
pecialgnetworkgofgfibersgcalledgthegPurkinjegfibers.gThesegfibersgspreadgfromgtheginterventricu
largseptumgintogthegpapillarygmuscles.gTheygcontinuegdownwardgtogthegapexgofgthegheart,gcom
posinggangelaborategwebgthatgpenetratesgaboutgonegthirdgofgthegwaygintogthegventriculargmuscl
egmass.gThegfibersgthengbecomegcontinuousgwithgthegmusclegcellsgofgthegrightgandgleftgventricl
es.
OBJ:g Describegtheglocation,gfunction,gand,gwhengappropriate,gthegintrinsicgrategofgthegfollowinggstruc
tures:gsinoatrialgnode,gatrioventriculargbundle,gandgPurkinjegfibers.
6. Ingthegheart’sgconductiongsystem,gtheg
receive(s)gangelectricalgimpulsegfromgthegrightgan
dgleftgbundlegbranchesgandgrelay(s)gitgtogthegventriculargmyocardium.
a. AVgnode
b. SAgnode
c. Purkinjegfibers
d. atrialgpacemakergcells
ANS:g C
Thegrightgbundlegbranchginnervatesgthegrightgventricle.gThegleftgbundlegbranchgspreadsgthegelect
ricalgimpulsegtogtheginterventriculargseptumgandgleftgventricle.
OBJ:g Describegtheglocation,gfunction,gand,gwhengappropriate,gthegintrinsicgrategofgthegfollowinggstruct
ures:gsinoatrialgnode,gatrioventriculargbundle,gandgPurkinjegfibers.
7. WhatgdoesgthegQRSgcomplexgrepresent?
a. Atrialgdepolarization
b. Ventriculargcontraction
c. Ventriculargrepolarization
d. Ventriculargdepolarization
ANS:g D
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Whengthegventriclesgaregstimulated,gagQRSgcomplexgisgrecordedgongthegECG.gThus,gthegQRS
gcomplexgrepresentsgventriculargdepolarization.gAtrialgdepolarizationgisginitiatedgbygthegSAgn
odegongthegwallgofgthegrightgatrium,gwhichgisgsymbolizedgbygthegPgwavegthatgshowsgongthegE
KG.gVentriculargcontractionghappensgwhengthegcardiacgmusclesgcontractgwithingthegventricles
,galthoughgthisgcontractiongisgrepresentedgbygthegQRSgongthegEKG,gthegmostgspecificganswergr
elatedgtogelectricitygingthegheartg(andgnotgheartgmuscle)gisgventriculargdepolarization.gVentricl
egrepolarizationgrepresentsgthegrelaxationgandgjourneygbackgtogisoelectricgbaseline,gwhichgcan
gincludegSTgsegmentgandgTgwave.
OBJ:g Definegandgdescribegthegsignificancegofgeachgofgthegfollowinggasgtheygrelategtogcardiacgelectric
algactivity:gPgwave,gQRSgcomplex,gTgwave,gUgwave,gPRgsegment,gTPgsegment,gSTgsegment,gPRgint
erval,gQRSgduration,gandgQTginterval.
8. Thegnormalgpacemakergofgthegheartgisgtheg node,gwhichgisgfoundgingtheg
atrium,gandghasgangintrinsicgfiringgrategofg beats/min.
a. sinoatrial;gleft;g40gtog60
b. sinoatrial;gright;g60gtog100
c. atrioventricular;gleft;g20gtog40
d. atrioventricular;gright;g100gtog180
ANS:g B
Thegsinoatrialg(SA)gnodegisgnormallygthegprimarygpacemakergofgthegheartgbecausegitghasgthegfa
stestgfiringgrategofgallgofgthegheart’sgnormalgpacemakergsitesg(60gtog100gbeats/min).gThegSA
nodegisglocatedgingtheguppergposteriorgpartgofgthegrightgatriumgwheregthegsuperiorgvenagcavagan
dgthegrightgatriumgmeet.
OBJ:g Describegtheglocation,gfunction,gand,gwhengappropriate,gthegintrinsicgrategofgthegfollowinggstruct
ures:gsinoatrialgnode,gatrioventriculargbundle,gandgPurkinjegfibers.
9. OngangECG,gwhatgisgthegfirstgnegativegdeflectiongseengaftergthegPgwave?
a. Qgwave
b. Rgwave
c. Sgwave
d. Tgwave
ANS:g A
AgQRSgcomplexgnormallygfollowsgeachgPgwave.gThegQRSgcomplexgbeginsgasgagdownwardgdef
lection—thegQgwave.gAgQgwavegisgalwaysgagnegativegwaveform.
OBJ:g Definegandgdescribegthegsignificancegofgeachgofgthegfollowinggasgtheygrelategtogcardiacgelectric
algactivity:gPgwave,gQRSgcomplex,gTgwave,gUgwave,gPRgsegment,gTPgsegment,gSTgsegment,gPRgint
erval,gQRSgduration,gandgQTginterval.
10. LeadgIIgrecordsgthegdifferencegingelectricalgpotentialgbetweengtheg leggandg arm.
a. left;gleft
b. left;gright
c. right;gleft
d. right;gright
ANS:g B
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