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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
Q

it is the remnant of sinus venosus

A

SA node

26
Q

true pacemaker

A

SA node

27
Q

where can the SA node be found

A

junct of RA and SVC

28
Q

conducting system of heart from SA to AV node

A

from SA node to internodal pathway of bachmann, wenckebach. thorel; these will connect the atrium and converge towards the AV node

29
Q

from AV node

A

from AV into bundle of his divide into left and right bundle branches

30
Q

right bundle branches vs left bundle branches

A

right bundle - right ventricle - purkinje

left - left ventricle - left anterior/posterior fascicles - purkinje

31
Q

describe the ECG

A

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
Q

why is the SA node the true pacemaker

A

frequency of impulse production is faster
greater rhythmicity depresses the rhythmicity of other potential pacemakers

33
Q

1st grade heart block

A

AV junction - 40-55 bpm - bawal exercise

34
Q

principle of overdrive suppresion

A

SA node has the fastest firing, therefore all the other pacemakers will be inhibited which also include the aberrant pacemaker

34
Q

2nd deg heart block

A

purkinje - 25-40 bpm - transplant/int pacemaker

34
Q

what are aberrant pacemakers

A

causes palpitations, arrythmia

35
Q

what are the factors that determine pacemaker discharge frequency

A

Rate or slope of depolarization during phase 4
Level of threshold potential which must be attained
Magnitude of resting potential

36
Q

what happens when you decrease the slope of pacemaker

A

tp will be reached slower; overshoot will be at later time

37
Q

what happens if u have a higher TP

A

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
Q

what factors affect pacemaker activity

A

ach nd vagal influence
sympathetic activity
temperature
ions

39
Q

how does ach nd vagal influence affect pacemaker activity

A

brady - decreases phase 4 slope - inc K conductance vua M2 MUSCARINIC
sinus arrest - vagal massage

40
Q

how does sympathetic activity affect pacemaker activity

A

inc hr - inc slope phase 4 - lower RMP - NE binds to beta1 - inc depol

40
Q

how does sympathetic activity affect pacemaker activity

A

inc hr - inc slope phase 4 - lower RMP - NE binds to beta1 - inc depol

41
Q

temp affect pacemaker activity

A

cool - dec hr - depressing slope phase 3
severe cooling - metabolism stops
heating - same as NE

42
Q

ions affect pacemaker activity

A

dec K - inc hr
hyperkalemia - RMP lowered - unexcitable
stops in diastole

43
Q

where do internodal tracts go to

A

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
Q

has slowest conduction velocity out of all cardiac tissues

A

AV node

45
Q

why is it that AV node is always at anterograde

A

Safety feature to prevent arrythmia

46
Q

where is the AV node found

A

beneath the endocardium on the (R) side of the atrial septum

47
Q

significance of AV nodal delay

A

ensures that the atria have ejected their blood into the ventricles first before the ventricles contract. - ventricular filling

48
Q

bundle of kent

A

15% of popu; fibers that bypass his - aberrant

49
Q

has fastest conduction velo

A

purkinje; 4 m/s

50
Q

relate diastole nd inc hr

A

hr inc - diastole dec - low sv - low co - hr goes higher - cardiac arrest

pt momints (10 decks)

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