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CardioPulm Final > Cardiac Action Potential > Flashcards

Cardiac Action Potential Flashcards

1
Q

What all does the AP from the SA node go through?

A

spreads throughout atria causing depolarization (RA slightly before LA); spreads down to the AV node

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2
Q

Describe the path of the AP from the AV node through the ventricles

A

AV node -> bundle of His -> right and left bundle branches in the interventricular septum -> down towards apex of heart and turns and moves back up along the lateral walls of the ventricles through Purkinje fibers

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3
Q

Why are nerve fiber sizes in the heart important? Describe the order from large to small

A

larger fibers have faster AP transmission & greater velocity

Purkinje fibers/bundle branches/bundle of His > atria and ventricular myocytes > AV node

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4
Q

What is the purpose of the conduction delay at the AV node?

A

to allow atria to completely empty into ventricles before ventricles contract

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5
Q

What is resting membrane potential of the SA node?

A

-65 +/- (-5)

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6
Q

What is resting membrane potential of the atria and ventricles?

A

-90 +/- (-5)

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7
Q

Describe Na (m) channels

A

voltage gated Na channels that open to depolarize the cell during phase 0 (activated when membrane potential crosses threshold); contribute to phase 1 as well (inactivation gates close)

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8
Q

Describe K (a) channels)

A

produce a transient outward current during phase 1; open briefly to cause partial repolarization (balancing act w/ Na (m) channels

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9
Q

Describe L type Ca channels

A

voltage gated Ca channels that open after depolarization spike and bring Ca into the cell; establish plateau of phase 2 w/ K (b) channels; closing causes phase 3

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10
Q

Describe K (b) channels

A

allow K out of cell except from phase 0 to phase 3; slow to close but prevent K from leaking out of cell too much as a result of Na influx

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11
Q

Describe K (c) channels

A

K leak channels are always open and contribute to resting membrane potential

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12
Q

Describe Na (f) channels

A

specific to the SA and AV nodes; cause slow depolarization during resting phase (allows nodes to have autonomous depolarization)

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13
Q

Describe K (d) channels

A

voltage gated K channels; open and release K during phase 3 (repolarization)

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14
Q

What causes phase 4 of the SA and AV nodes? What happens if the slope changes?

A

Phase 4 caused by Na (f) channels

If slope increases -> faster depolarization
If slope decreases -> slower depolarization

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15
Q

What causes phase 0 of SA/AV node?

A

L type Ca channels open (Ca influx) and K (b) channels close

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16
Q

What causes phase 3 of SA/AV node?

A

closing of L type Ca channels and opening of K (b) channels (reverse of phase 0)

17
Q

What do fast tissues involve for cardiac AP?

A

myocytes and Purkinje fibers

18
Q

What sustained resting membrane potential in phase 4 of fast tissues?

A

K (c) channels - leak channels continuously allow K out of cell

19
Q

What causes phase 0 of fast tissues?

A

depolarization caused by crossing threshold; voltage gated Na (m) channels open

20
Q

What causes phase 1 of fast tissues?

A

small repolarization caused by Na (m) channels closing and K (a) channels opening -> pulls potential down a little bit

21
Q

What causes phase 2 of fast tissues?

A

plateau phase -> sustained by slow opening of L type Ca channels which delays repolarization; balances w/ closure of K (b) channels to maintain plateau (sustain contraction)

22
Q

What causes phase 3 of fast tissues?

A

complete repolarization caused by closing of L type Ca channels and reopening of K (b) channels and opening of voltage gated K (d) channels

23
Q

What is absolute refractory period (ARP)?

A

no depolarization can occur

24
Q

What is relative refractory period (RRP)?

A

when an AP can be generated but the cell will have abnormal conduction (AP is weaker)

25
Q

What is supernormal period (SNP)?

A

when the cell is more excitable than normal but will have a lower phase 0 slope (slower velocity)

26
Q

Describe chronotropic effect

A

changes rate of depolarization of SA node (affects HR)

Positive = faster HR
Negative = slower HR
27
Q

Describe dromotropic effect

A

changes speed of conduction

Positive = increased speed
Negative = decreased speed
28
Q

Describe inotropic effect

A

changes strength of muscular contraction

Positive = heart contracts harder
Negative = heart contracts softer
29
Q

Describe lusitropic effect

A

changes rate of muscular relaxation

Positive = increased relaxation
Negative = decreased relaxation
30
Q

What carries parasympathetic fibers to the SA and AV nodes? Describe the receptors and NT involved in parasympathetics of the heart

A

Vagus N. carries parasympathetics to SA and AV node

NT = ACh
Receptor = muscarinic (M2 or M3)
31
Q

Describe the receptors and NT involved in sympathetics of the heart

A 
NT = NE
Receptor = B1-andrenergic receptor

CardioPulm Final (8 decks)

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