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Physiology > Cardiac Mechanics and EKG > Flashcards

Cardiac Mechanics and EKG Flashcards

1
Q

pacemaker cells

A

initiate depolarization, autorhythmic

SA node, AV node, purkinje fibers

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2
Q

contractile cells

A

forceful contraction

myocardium

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3
Q

what helps the heart to function as one unit?

A

gap junctions by sending charge on to the next quickly

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4
Q

phase 0 action potential cardiac

A

depolarization

voltage gated Na channels

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5
Q

phase 1 action potential cardiac

A

initial repolarization

closing VGNa

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6
Q

phase 2 action potential cardiac

A

plateau

opening VGCa

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7
Q

phase 3 action potential cardiac

A

repolarization

opening VGK

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8
Q

phase 4 action potential cardiac

A

resting membrane potential

K+ leak channels

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9
Q

what changes during action potential in cardiac muscle cells?

A

permeability

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10
Q

absolute refractory period

A

0.2-0.25 s

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11
Q

relative refractory period

A

0.05 s

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12
Q

do skeletal muscles or cardiac muscles have longer refractory periods?

A

cardiac muscles

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13
Q

what is the mechanism of cardioplegic solution?

A

increases extracellular K+

depolarizes and then cannot repolarize

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14
Q

two ways to alter contraction

A

augmenting force

decreasing force

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15
Q

two ways to augment force of contraction

A 
increase calcium (beta agonist)
sensitizing contractile machinery
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16
Q

how does the beta agonist increase calcium?

A

activates PKA that phosphorylates VGCC and makes them more likely to be open

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17
Q

way to decrease force of contraction

A

decrease calcium

beta blocker

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18
Q

what is special about pacemaker cells

A

contain fewer contractile fibers
no organized sarcomeres
faster conducting rate

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19
Q

If- funny current other name

A

hyperpolarization activated cyclic nucleotide gated

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20
Q

funny current mechanism

A

resting potential is unhill curve and is caused by leaky sodium current

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21
Q

which action potential phase is absent in SA and AV nodes compared to cardiac muscle cells

A

phase 2

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22
Q

intrinsic depolarization rate SA node

A

60-80bpm

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23
Q

intrinsic depolarization rate AV node

A

40-55bpm

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24
Q

intrinisic depolarization rate purkinje fibers

A

15-35bpm

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25
Q

what type of cells have funny current?

A

pacemaker

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26
Q

chronotropic

A

increase heartrate

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27
Q

lusitropic

A

increase rate of relaxation

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28
Q

phospholambin

A

inhibits SERCA

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29
Q

beta 1 agonist

A

increases HR by increasing cAMP

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30
Q

what nerve is the parasympathetic mediated through?

A

vagus nerve

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31
Q

2 ways that parasym works to decrease HR

A

increases K+ current (hyperpolarize)

inhibits AC and decreases cAMP and PKA

32
Q

conduction velocity SA node

A

1m/s

33
Q

conduction velocity AV node

A

0.05 m/s

34
Q

total time from SA node to bundle branch

A

0.16

35
Q

conduction velocity purkinje fibers

A

1.5-4.0m/s

36
Q

conduction velocity muscle cells

A

0.3-0.5 m/s

37
Q

4 common inotropic agents used for short term HF

A

digitalis(digoxin)
dobutamine
milrinone
levosimendan

38
Q

What is digoxin mechanism of action

A 
inhibits NaK pump
increases Ca
slows conduction of AV node
depresses SA node
does NOT increase HR
39
Q

dobutamine mechanism of action

A

beta 1 agonist
increases Ca
increases HR

40
Q

milrinone mechanism of action

A

phophodiesterase 3 inhibitor
increases cAMP
increases Ca
increases HR

41
Q

levosimendan mechanism of action

A

increases Ca sensitization of troponin C
does not increase HR
does NOT cause arrhythmias

42
Q

1 large box ECG = __ mV?

A

0.5mV

43
Q

1 large box ECG= __ sec?

A

0.2 sec

44
Q

how many large boxes = 1sec?

A

5 large boxes

45
Q

normal P-R interval length

A

<0.2 sec (< 1 large box)

46
Q

normal QRS complex width?

A

<3 small boxes

47
Q

what does the height of the QRS complex indicate?

A

muscle mass

48
Q

What can cause a wide QRS?

A

bundle branch block

49
Q

normal QT interval

A

0.35-0.42s

50
Q

QTc

A

corrected QT interval

51
Q

hypocalcemia effect on QT interval

A

long

52
Q

hyercalcemia effect on QT interval

A

short

53
Q

what is the ion channel involved in prolonged QT interval due to genetics?

A

K+

54
Q

What usually causes ST segment changes?

A

MI

STEMI

55
Q

what do ECGs measure

A

the potential difference between two leads
(outside the cardiomyocytes)
this is why it is positive

56
Q

what does an ECG read when the heart is at rest?

A

0

57
Q

what does the lead two measure

A

QRS complex

58
Q

why is the QRS complex positive?

A

the negative lead has more neg charges around it and positive lead has more pos charges around it

59
Q

during repolarization of the ventricles what repolarizes first?

A

last area to depolarize is the first to repolarize

epi to endo

60
Q

t wave

A

repolarization of the ventricle

61
Q

why would the t wave be inverted

A

if the first area to depolarize is the first area to repolarize

62
Q

what are the causes of inverted t wave

A

coronary ischemia
hypertrophy
bundle branch block

63
Q

bradycardia speed/ causes

A

<60bpm

vagal nerve stimulation, athlete, cold temp

64
Q

SA block

A

missed beat

65
Q

AV block causes

A

vagal stimulation
ischemia
calcification
inflammation

66
Q

wenckebach

A

AV block 2nd degree type 1 (longer and longer)

67
Q

tachycardia

A

> 100bpm

68
Q

tachycardia causes

A 
sympathetic nerve stimulation
epi
drugs
increased temp
hyperthyroidism 
blood loss
fever
69
Q

supraventricular tachycardia rate

A

100-250 bpm

70
Q

How to help reduce SVT?

A

adenosine

vagal maneuvers

71
Q

torsade de pointes

A

looks like a ribbon
twisting of the QRS
prolonged QT syndrome
moves to Vfib

72
Q

causes of premature contractions

A

ischemia
calcification
chemicals
genetic

73
Q

causes of premature ventricular contractions

A

MI/ ischemia

drugs that cause excitability

74
Q

treatment for afib

A

antiarrhythmics
anticoagulants
ablation
electrical cardioversion

75
Q

mean QRS axis deviation

A

right or left BBB

hypertrophy

Physiology (13 decks)

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