Classic Classic Quiz Cardiology : Action Potentials by Tommymoran Tommymoran 2 025 played - 10 yrs ago Prep for First Cardiology Midterm QUIZ 30 QUESTIONS hard 1 What is the correct pathway for the heart's conducting system? SA Node->AV Node->Atrial Muscle->AV Bundle->Purkjine Fibres->Ventricular MuscleSA Node->AV Node->AV Bundle->Purkinje Fibres->Atrial Muscle->Ventricular MuscleSA Node->Atrial Muscle->AV Node->AV Bundle->Ventricular Muscle->Purkinje FibresSA Node->Atrial Muscle->AV Node->AV Bundle->Purkinje Fibres-Ventricular Muscle 2 The Sinoatrial (SA) Node is... A defined-cluster of conducting-myocytes on the right atriumA diffuse nodule of myocytes at the Superior Vena Cava-Right Atrium junctionA defined-nodule of specialized-conducting cells at the Inferior Vena Cava-Right Atrium JunctionA diffuse nodule of specialized-conducting cells at the Superior Vena Cava-Right Atrium junction 3 The following is an action potential representative of what class of cells? SA Nodal CellsMyocytesNerve CellA and C 4 Which phase in the graph below constitutes the "pacemaker potential? " Phase 0Phase 3Phase 4None of the above 5 What is the resting potential of an SA Nodal cell? -60mV-70mV-90mVNone of the above 6 The action potential in SA Nodal cells is primarily driven by... Fast Na+ currentsSlow Ca++ currentsSlow K+ currentsNone of the above 7 The slow depolarization apparent in phase 4 is primarily due to. . The slow L-type Ca++ ChannelA slow, inward Na+ current (funny current)A slow, outward Na+ current (funny current)None of the above 8 What is the function of T-type Ca++ channels? Open for a long period, resulting in the majority of the cells depolarization in Phase 0Open transiently in phase 3, to reinstitute calcium stores lost in phase 0Open for a long period of time in phase 4, to reinstitute calcium stores lost in phase 0Open transiently, allowing Ca++ influx to further depolarize the cell in phase 4 9 Funny currents persist... At all times throughout SA Nodal cell AP propagationOnly when an SA Nodal cell is hyperpolarizedOnly during the repolarization of an SA Nodal cellNone of the above. 10 What primarily causes the repolarization in Phase 3? A hyperpolarizing outward K+ currentClosing of the L-type Ca++ channelsOpening of the slow acting Na+ channels (funny current)A and B 11 What would be one result of hypokalemia in SA nodal cells? Decreased rate of repolarization, leading to Early AfterDepolarizations (EADs) and arrythmiaIncreased rate of repolarization, leading to Early AfterDepolarization (EADs)Hypoexcitability to due decreased rate of K+ rectifier functionNone of the above 12 What is the intrinsic automaticity of the SA node? 80 beats/minute100 beats/minute120 beats/minuteNone. The heart cannot beat without outside stimuli. 13 What type of receptor helps to directly control heart rate? Cholinergicß1-AdrenergicNMDAA and B 14 ß-adrenergic receptors associate with G-proteins. Upon ligand binding, which subunit will bind to and activate adenylyl cyclase? Alpha-(s)-subunitß-subunitGamma-subunitB and C 15 Activated adenylyl cyclase cleaves ATP in cAMP, resulting in what? Increased activation of Hyperpolarization-activated cyclic nucleotide-gated (HCN) channelsEarlier L-type Ca++ channel openingAccelerated RepolarizationAll of the above 16 Cholinergic receptors are associated with a G-protein constituted by the inhibitory alpha-(i)-subunit. Upon decreased cAMP levels, what important kinase activity is deterred? PKA phosphorylation of adenylyl cyclasePKB phosphorylation of HCN channelsPKA phosphorylation of L-type Ca++ channelsB and C 17 What ß-gamma G-protein subunit interaction may counteract the funny current? Potassium channel interactionHCN channel interactionNa+/Ca++ exhcanger interactionNone of the above 18 What is the function of the AV node? Limit fibrillation entry into ventriclesServe as back-up pacemakerDelay action potential to allow ventricular filling (function as switching-station)All of the above 19 Which has the faster intrinsic automaticity (rate of cycle)? SA NodeAV NodeThey are the sameRandom filler answer (pick this if you want to be wrong) 20 What is the function of the delayed action potential in the AV node, compare to that of a Purkinje Fibre, illustrated below? Separate heart beats to reduce heart stressAllow for atrial fillingAllow for ventricular fillingThere is no function. B is the representation of a pathologic AP 21 What characteristic of the AV Node and AV bundle result in the slower generation of action potential compared to Purkinje Fibres? Fewer channels to exchange ionsGenerally, smaller and slower ion channelsDenser and less symmetric cellular morphologyA and B 22 Connexins, intercellular pores, allow the exchange of Na+ ions between cells. What characteristic would you expect of Connexins of the SA and AV nodes compared to Purkinje Fibres? Smaller diameterLarger diameterSlow-conductanceA and C 23 What allows the ventricles to contract as a syncitium? Fast conducting NaV1. 5 channelsFast-acting bundle branchesPurkinje fibre connectionsA and C 24 What ion exchange predominantly drives depolarization in Purkinje Fibres and myocytes? Na+ influx by NaV1. 5 channelsCa++ influx by fast-acting Ca++ channelsHCN funny currentNone of the above 25 Connexin 40 is important for? Fast propagation of AP in Bundle branchesFast propagation of AP in Purkinje FibresA and BNone of the above 26 What is atrial fibrillation Reduced firing of speciliazed-conducting cells of in the SA nodeRapid firing of speciliazed-conducting cells of in the SA nodeRapid firing of myocytes in the atriumB and C 27 What are possible side-effects of anti-arrhythmic drugs, such as Amiodarone (pacerone)? Corneal deposits (Halo-vision)Hyper- or hypo- thyroidismSunburns from trivial exposureAll of the above 28 Should medical management with anti-arrhythmic drugs be ineffective, what is an appropriate follow-up procedure? Anti-thrombotic treatmentBi-weekly defibrillationsAblation and installment of artificial pacemakerNone of the above 29 What is sick sinus syndrome? The failure of the SA node to response to extra-cardiac stimuliThe stoppage of all action potential within the SA nodeA collection of arrhythmic conditions originating from the SA nodeAll of the above 30 Why is Tbx18 transfection a potentially attractive treatment for Atrial Fibrillation? By converting cardiomyocytes in to pacemaker cells, it may restore SA node functionWill respond to sympathetic stimuliTbx18 is found endogenously at highly levels in the adult heartA and B A mistake in this Quiz ? Contact the author Commentaires
