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CPR Exam 1 > Cardiac AP and conduction > Flashcards

Cardiac AP and conduction Flashcards

1
Q

An AP spreads in the heart in what general order?

A

1) SA node
2) AV node
3) Bundle of His
4) Right/left bundle branch
5) Purkinje fibers

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2
Q

Rank the conduction velocity of the atria, AV node, Purkinje fibers, and ventricle from fastest to slowest

A

1) Purkinje
2) Atria and ventricle
3) AV node

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3
Q

Which atrium contracts first?

A

Right

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4
Q

Which layer of the heart contracts first?

A

Endocardium prior to epicardium

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5
Q

Which ventricle epicardium contracts first?

A

Right ventricle epicardium

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6
Q

What ion is important for the refractory periods?

A

Sodium

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7
Q

The inward calcium current via L-type calcium channels are responsible for what phase of an AP?

A

Phase 2

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8
Q

The transient outward potassium current via potassium channels are partially responsible for what phase of an AP?

A

Phase 1

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9
Q

The voltage-gated potassium channels and outward potassium current are responsible for transition from what phases?

A

Phase 2 into phase 3

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10
Q

The combination of inward calcium current, outward potassium current and inward rectifiers contribute to?

A

Phase 2

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11
Q

What state are the K+ leak channels during phase 2?

A

Increased current outward

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12
Q

In what phase are the SA node and AV node resting membrane potential gradually depolarizing until it reaches threshold?

A

Phase 4

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13
Q

In the SA and AV node, what phase is there opening of voltage gated calcium channels rather than voltage gated sodium channels and closure of voltage gated potassium channel?

A

Phase 0

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14
Q

In the SA and AV node, what phase is there reversal of phase 0 where there is closure of voltage gated calcium channels and opening of voltage gated potassium channels?

A

Phase 3

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15
Q

What period can no AP be generated?
What period can an AP be generated but requires greater stimulus and/or abnormal conduction?
What period is the new cell more excitable than normal and easier to generate AP and may have abnormal conduction?

A

1) Absolute refractory
2) Relative refractory
3) Supranormal period

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16
Q

If the cell is stimulated during RRP or SNP conduction of the AP will be?

A

Weaker

17
Q

Negative chronotropic effects can lead to?

A

1) Slower opening of sodium channels during phase 4

2) Hyperpolarization of SA node

18
Q

Negative dromotropic effects can lead to?

A

1) Reduced inward calcium current

2) Increasing outward potassium current

19
Q

What is the NT for sympathetic stimulus?

What is the receptor?

A

1) Norepinephrine

2) Beta 1 adrenergic

20
Q

What is the NT for parasympathetic stimulus?

What is the receptor?

A

1) Ach

2) Muscarinic (M2/M3)

21
Q

Positive chronotropic effects can lead to?

A

Rapid opening of sodium channels during phase 4

22
Q

Positive dromotropic effects can lead to?

A

Increased inward calcium current to increase speed of conduction

23
Q

What effect does sympathetic stimulation of HR have on sodium?
Parasympathetic stimulation?

A

1) Increase inward sodium

2) decrease inward sodium

24
Q

During which phase of an AP is the membrane potential closest to the potassium equilibrium potential throughout that phase?

A

Phase 4

25
Q

Administration of a Kv11.1 channel mediated rapid potassium current blocker would have what effect?

A

Prolonged phase 2

26
Q

Administration of atropine, and M2 receptor blocker, would have what effect?

A

Increase sodium conductance

27
Q 
What is phase 0?
Phase 1?
Phase 2?
Phase 3?
Phase 4?
A

1) Depolarization
2) Partial repolarization
3) Plateau
4) Repolarization

28
Q

When an MI causes the SA node to no longer function and the AV node now sets the pace of the heart, what best describes the change seen in the heart?
Activation of which receptor would generate an AP that looks similar to the AP seen in this patient?

A

1) Negative chronotropic effect

2) Muscarinic receptors

29
Q

The slow conduction through the AV nodes is to allow sufficient time for?

A

Filling of the ventricles

30
Q

Which phase of the AP helps ensure that the heart doesn’t go into fibrillation (arrhythmia)?

A

Refractory period

31
Q

What structures in the heart have pacemaker capability?

A

1) SA node
2) AV node
3) Purkinje fibers

32
Q

What is the resting membrane potential for a normal cardiac myocyte?
For a SA nodal myocyte?

A

1) -95

2) -65

33
Q

Do ventricular myocytes or atrial myocytes have a shorter AP?

A

Atrial

34
Q

How does Ach slow the HR?

A

1) They affect potassium channels and keep them open slowing phase 0 in the SA node
2) Slows down Na channels elongating phase 4

35
Q

What would a negative lusitropic effect cause?

A

Longer duration of relaxation of cardiac muscles

CPR Exam 1 (27 decks)

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