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pt momints > PHYSIO-LEC: Cardiac Electrophysiology > Flashcards

PHYSIO-LEC: Cardiac Electrophysiology Flashcards

1
Q

what is the functional connection between cardiac muscle cells

A

intercalated discs

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2
Q

compare the striations of cardiac to skeletal

A

cardiac are arranged in series = irregular striations

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3
Q

what is the significance of mitochondria

A

heart requires a lot of energy = plenty mitochondria

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4
Q

why is there no room for anaerobic metabolism

A

if anaerobic angina sets in and may lead to cardiac arrest; always aerobic

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5
Q

slow response AP is exhibited by

A

SA, AV and junctional areas

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6
Q

explain the ionic exchange during slow response AP

A

prepotential: caused by transient opening of Ca channels; goes towards depol

spike potential: after it reaches firing level; more Ca opens = AP

Overshoot: goes over 0 as more Ca enters; as it reached the peak Ca closes

K channels open to start repol and closes after repol

Funny current: initiates prepotential; stimulates opening of transient Ca; Na leaks into pacemaker cell

cycle repeats

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7
Q

what are the phases of slow response AP

A

0: depol
3: repol
4: back to RMP; prepotential

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8
Q

fast response AP is exhibited by

A

atrial/ventricular muscles, fiber tracts, purkinje fibers

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9
Q

this refers to the standard cardiac potential

A

fast response ap

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10
Q

what is the RMP of fast response AP

A

-90 mV

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11
Q

what is the RMP of slow response AP

A

-50 to -65 mV

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12
Q

explain the phases of fast response AP

A

0: influx of Na; causes a spike potential - overshoot once firing level is reached

1: upon reaching peak Na channels close and K open; initial repol

2: opening of Ca overwhelms Ka = plateau

3: final repol bc of continuous opening Ka channels; close as repol is reached

4: going back to RMP due to Na-K pump

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13
Q

explain the genesis of plateau

A

influx of Ca is counterbalanced by K = plateau; influx of Ca is involved in excitation-contraction coupling

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14
Q

explain the restorations of ionic concentrations

A

via Na-K pumps; 3 Na in - 1 Ca out

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15
Q

how much ATP does the heart require

A

1 ATP for power stroke and 3 ATP for restorations of ionic conce; 4 ATP

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16
Q

it is the notch in phase 1 - peak

A

cardiac notch

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17
Q

tetrodotoxin in fast response AP

A

once introduced it makes fast response into slow; if transmission slows down hr decs = less CO = heart failure

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18
Q

compare slow vs fast response AP

A

slow: sa node, 0,3,4; no NA

fast: purjinke; 0-4; NA is involved

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19
Q

ap will alwayd precede …

A

muscle twitch

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20
Q

what does absolute RP do

A

prevents re entry of AP for steady hr

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21
Q

when does absolute RP occur

A

onset of depol to 1/3 phase 3

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22
Q

what does relative RP do

A

allows a stronger stimulus to initiate AP; hr gets faster

23
Q

where can the supranormal period be found

A

just after relative refractory period in fast graph

24
Q

what is the supranormal period mean

A

stimulus less than thresholds elicit AP; must be avoided when using defibrilator bc v tach/fib will occur

25
it is the remnant of sinus venosus
SA node
26
true pacemaker
SA node
27
where can the SA node be found
junct of RA and SVC
28
conducting system of heart from SA to AV node
from SA node to internodal pathway of bachmann, wenckebach. thorel; these will connect the atrium and converge towards the AV node
29
from AV node
from AV into bundle of his divide into left and right bundle branches
30
right bundle branches vs left bundle branches
right bundle - right ventricle - purkinje left - left ventricle - left anterior/posterior fascicles - purkinje
31
describe the ECG
P wave - atrial depolarization which is in line with atrial muscle depolarization QRS - ventricular depolarization which is in line with fast response AP in ventricles T wave - ventricular repolarization which is in line with phase 3 of fast response U wave - ventricular filling; found in diastole
32
why is the SA node the true pacemaker
frequency of impulse production is faster greater rhythmicity depresses the rhythmicity of other potential pacemakers
33
1st grade heart block
AV junction - 40-55 bpm - bawal exercise
34
principle of overdrive suppresion
SA node has the fastest firing, therefore all the other pacemakers will be inhibited which also include the aberrant pacemaker
34
2nd deg heart block
purkinje - 25-40 bpm - transplant/int pacemaker
34
what are aberrant pacemakers
causes palpitations, arrythmia
35
what are the factors that determine pacemaker discharge frequency
Rate or slope of depolarization during phase 4 Level of threshold potential which must be attained Magnitude of resting potential
36
what happens when you decrease the slope of pacemaker
tp will be reached slower; overshoot will be at later time
37
what happens if u have a higher TP
threshold potential will be reached at a very later time before we reach the firing level and produce an overshoot, causing the heart rate to decrease, causing further bradycardia
38
what factors affect pacemaker activity
ach nd vagal influence sympathetic activity temperature ions
39
how does ach nd vagal influence affect pacemaker activity
brady - decreases phase 4 slope - inc K conductance vua M2 MUSCARINIC sinus arrest - vagal massage
40
how does sympathetic activity affect pacemaker activity
inc hr - inc slope phase 4 - lower RMP - NE binds to beta1 - inc depol
40
how does sympathetic activity affect pacemaker activity
inc hr - inc slope phase 4 - lower RMP - NE binds to beta1 - inc depol
41
temp affect pacemaker activity
cool - dec hr - depressing slope phase 3 severe cooling - metabolism stops heating - same as NE
42
ions affect pacemaker activity
dec K - inc hr hyperkalemia - RMP lowered - unexcitable stops in diastole
43
where do internodal tracts go to
Anterior Tract of Bachman o goes to (L) atrium * Middle Tract of Wenckebach * Posterior Tract of Thorel o Spread of excitation from atria to ventricles o converge to the AV Node
44
has slowest conduction velocity out of all cardiac tissues
AV node
45
why is it that AV node is always at anterograde
Safety feature to prevent arrythmia
46
where is the AV node found
beneath the endocardium on the (R) side of the atrial septum
47
significance of AV nodal delay
ensures that the atria have ejected their blood into the ventricles first before the ventricles contract. - ventricular filling
48
bundle of kent
15% of popu; fibers that bypass his - aberrant
49
has fastest conduction velo
purkinje; 4 m/s
50
relate diastole nd inc hr
hr inc - diastole dec - low sv - low co - hr goes higher - cardiac arrest

pt momints (10 decks)

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