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Quiz Animals
Cardiology : Action Potentials
created by
tommymoran
on 4 Feb 14, enabled by
Lou
Animals
Hard level
(41% of success)
30 questions - 1 092 players
Prep for First Cardiology Midterm
1
What is the correct pathway for the heart's conducting system?
SA Node->AV Node->Atrial Muscle->AV Bundle->Purkjine Fibres->Ventricular Muscle
SA Node->AV Node->AV Bundle->Purkinje Fibres->Atrial Muscle->Ventricular Muscle
SA Node->Atrial Muscle->AV Node->AV Bundle->Ventricular Muscle->Purkinje Fibres
SA 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 atrium
A diffuse nodule of myocytes at the Superior Vena Cava-Right Atrium junction
A defined-nodule of specialized-conducting cells at the Inferior Vena Cava-Right Atrium Junction
A 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 Cells
Myocytes
Nerve Cell
A and C
4
Which phase in the graph below constitutes the "pacemaker potential? "
Phase 0
Phase 3
Phase 4
None of the above
5
What is the resting potential of an SA Nodal cell?
-60mV
-70mV
-90mV
None of the above
6
The action potential in SA Nodal cells is primarily driven by...
Fast Na+ currents
Slow Ca++ currents
Slow K+ currents
None of the above
7
The slow depolarization apparent in phase 4 is primarily due to. .
The slow L-type Ca++ Channel
A 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 0
Open transiently in phase 3, to reinstitute calcium stores lost in phase 0
Open for a long period of time in phase 4, to reinstitute calcium stores lost in phase 0
Open transiently, allowing Ca++ influx to further depolarize the cell in phase 4
9
Funny currents persist...
At all times throughout SA Nodal cell AP propagation
Only when an SA Nodal cell is hyperpolarized
Only during the repolarization of an SA Nodal cell
None of the above.
10
What primarily causes the repolarization in Phase 3?
A hyperpolarizing outward K+ current
Closing of the L-type Ca++ channels
Opening 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 arrythmia
Increased rate of repolarization, leading to Early AfterDepolarization (EADs)
Hypoexcitability to due decreased rate of K+ rectifier function
None of the above
12
What is the intrinsic automaticity of the SA node?
80 beats/minute
100 beats/minute
120 beats/minute
None. The heart cannot beat without outside stimuli.
13
What type of receptor helps to directly control heart rate?
Cholinergic
ß1-Adrenergic
NMDA
A and B
14
ß-adrenergic receptors associate with G-proteins. Upon ligand binding, which subunit will bind to and activate adenylyl cyclase?
Alpha-(s)-subunit
ß-subunit
Gamma-subunit
B and C
15
Activated adenylyl cyclase cleaves ATP in cAMP, resulting in what?
Increased activation of Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels
Earlier L-type Ca++ channel opening
Accelerated Repolarization
All 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 cyclase
PKB phosphorylation of HCN channels
PKA phosphorylation of L-type Ca++ channels
B and C
17
What ß-gamma G-protein subunit interaction may counteract the funny current?
Potassium channel interaction
HCN channel interaction
Na+/Ca++ exhcanger interaction
None of the above
18
What is the function of the AV node?
Limit fibrillation entry into ventricles
Serve as back-up pacemaker
Delay 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 Node
AV Node
They are the same
Random 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 stress
Allow for atrial filling
Allow for ventricular filling
There 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 ions
Generally, smaller and slower ion channels
Denser and less symmetric cellular morphology
A 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 diameter
Larger diameter
Slow-conductance
A and C
23
What allows the ventricles to contract as a syncitium?
Fast conducting NaV1. 5 channels
Fast-acting bundle branches
Purkinje fibre connections
A and C
24
What ion exchange predominantly drives depolarization in Purkinje Fibres and myocytes?
Na+ influx by NaV1. 5 channels
Ca++ influx by fast-acting Ca++ channels
HCN funny current
None of the above
25
Connexin 40 is important for?
Fast propagation of AP in Bundle branches
Fast propagation of AP in Purkinje Fibres
A and B
None of the above
26
What is atrial fibrillation
Reduced firing of speciliazed-conducting cells of in the SA node
Rapid firing of speciliazed-conducting cells of in the SA node
Rapid firing of myocytes in the atrium
B and C
27
What are possible side-effects of anti-arrhythmic drugs, such as Amiodarone (pacerone)?
Corneal deposits (Halo-vision)
Hyper- or hypo- thyroidism
Sunburns from trivial exposure
All of the above
28
Should medical management with anti-arrhythmic drugs be ineffective, what is an appropriate follow-up procedure?
Anti-thrombotic treatment
Bi-weekly defibrillations
Ablation and installment of artificial pacemaker
None of the above
29
What is sick sinus syndrome?
The failure of the SA node to response to extra-cardiac stimuli
The stoppage of all action potential within the SA node
A collection of arrhythmic conditions originating from the SA node
All 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 function
Will respond to sympathetic stimuli
Tbx18 is found endogenously at highly levels in the adult heart
A and B
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