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CPR > Cardiac Conduction > Flashcards

Cardiac Conduction Flashcards

1
Q

What is the value for a first degree AV block?

A

greater than 0.2 ms

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2
Q

What order does AP spread? (general)

A
  • SA node
  • AV node
  • Purkinjie fibers
    • bundle of his
    • r/l bundle branches
    • smaller purkinjie fibers
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3
Q

Which contracts first:

  • RA or LA
  • Epicardium or Endocardium
  • LV epicardium or RV epicardium
A
  • RA before left
  • Endocardium before epi
  • RV epicardium before LV
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4
Q

What are second degree AV blcoks?

A
  • AV recieves signal and drops it, then receieves second signal and passes it on
  • Drop signal and pass every time
  • Random
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5
Q

Phase 4?

A

RMP, maintained by Na/K ATPase

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6
Q

What is phase 0 of the cardiac fast AP?

A
  • Results from reaching threshold
  • Incrased conductance of Na
  • Opening voltage gated fast Na channels (activation gate)
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7
Q

What is cardiac fast action potential phase 1?

A
  • Closure of voltage gated Na channels, Inactivation gates are closed (Ina)
  • Opening of transient outward K current (Ito)
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8
Q

What is the cardiac fast AP phase 2?

A
  • Opening of voltage gated L type Ca channels (Ica)
  • CLlosure of inward rectifying K channels (Ik1)
  • Closure of channels causing Ito
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9
Q

WHat is the cardiac fast AP phase 3?

A

Repolarization

  • CLosure of voltage gated L type Ca channels
  • Opening inward rectifying K channels
  • Opening of vooltage gated K channels (Ikr, Iks) these do start to open during phase 2 but largely contribute to phase 3
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10
Q

What happens if phase 3 is disrupted?

A
  • Ikr and Iks are not acting properly and Long QT syndrome result
  • transition from phase 2 to 3 is lengthened
  • can be ocngenital or acquired
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11
Q

What is cardiac slow AP phase 4?

A
  • Resting mem pot gradually depolarizes until it reaches threshold, intrinsic spontaneous depolarization acts as the pace maker
  • Due to the slow influx of Na through “funny” voltage gated Na channels (Inaf) that open upon complete repolarization of membrane
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12
Q

What is phase 0 of the cardiac slow AP?

A
  • Opening of voltage gated Ca channels
    • Rather than fast voltage gated Na channels
  • Closure of inward rectiying K channels
  • Phase one and two are absent in cardiac slow AP
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13
Q

What is phase 3 of the slow cardiac AP?

A
  • Reversal of phase 0
  • Closure of votage gated Ca channels
  • Opening delayed rectifying K channels
  • Closure of inward rectifying K channels
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14
Q

Parasympathetic stimuli to the heart is carried by ___ to the: __

A

Parasympathetic stimuli to the heart is carried by Vagus to the:

  • SA and AV node
  • Modest but physiologically insignifacant to atrial myocytes
  • Ach
  • Receptos M2/M3
  • Also special K ach channel
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15
Q

What is a negative chronotropic effect?

A
  • Slower entry of Na through funny Na channels during phase 4
  • Hyperpolarizationi of SA node by increasing outward K current via special K ach channels
  • NO influence on contractility
  • Takes longer to reach threshold and fire (slowing heart rate!)
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16
Q

Where does SNS go?

A
  • SA and AV node and ventricular myocytes
  • Not relevant in atrial myocytes
  • Norepi
  • Receptor B1 adrenergic
17
Q

What is a positive chronotropic effect?

A
  • Speeding up heart rate via rapid influx of Na through funny Na channels
    • allows threshold to be reached quicker
  • Increases contractilitiy (positive iontropic effect)
    • increases ca into myocytes
18
Q

What is a positive dromotropic and lusitropic effect?

A
  • Increased conduction velocity and relaxation velocity
    • greater phase 0 slope more rapid and complete recycling of AP
19
Q

What is the cardiac refractory period?

A
  • Period when AP can’t be generated
  • Refractory periods are longer to protect against arrhythmias and aid in rhythmic contraction
20
Q

What is an absolute refractory period?

A
  • No AP can be generated
  • all voltage gated Na channels are inactivated
21
Q

What is a relative refractory period?

A
  • AP can be generated but will require greater stimulus or have abnormal conduction
    • many but not all voltage gated Na channels have reset
22
Q

What is a supranormal period?

A
  • Cells are more excitable than normal and the AP will be abnormally conducted
    • closer to threshold, many Na channels are reset
23
Q

How does hyperkalemia impact cardiac AP?

A
  • Slows phase 0
  • Speeds up phase 3
  • Some cells may already be at threshold and others are very close to it, can result in asynchronyous contraction
24
Q

How does hypokalemia impact cardiac AP?

A
  • Were further from threshold and more stimulus is needed to depolarize
25
Q

How does S1 relate to EKG?

A
  • Q wavebegins as mitral valve closes
26
Q

How does S2 relate to EKG?

A
  • Its at the end of the T wave when the aortic valve closes
27
Q

How does S3 relate to the EKG?

A
  • Mitral valve opens and blood enters ventricles
28
Q

How does S4 relate to EKG?

A

PR segment

CPR (18 decks)

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