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CVPR Exam I > 5. Cardiac Ion Channels & Action Potentials > Flashcards

5. Cardiac Ion Channels & Action Potentials Flashcards

1
Q

The slow cardiac APs have a slow _____.

A

rising phase

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2
Q

Why is electrical activity important in the heart?

A
  1. generates repetitive firing in pacemaker cells 2. is a trigger for contraction
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3
Q

What slows the heart rate from the intrinsic rate of 100 bpm to the normal rate of 60-80bpm?

A

parasympathetic tone

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3
Q

What are the 2 types of calcium channels called?

A

L-type or T-type

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4
Q

Fast cardiac APs arise from _____, _____, and _____.

A

in the myocardial cells (atrium and ventricle muscles) and in the conductive pathways, perkinge fibers

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5
Q

The slow cardiac APs arise from the ____ and ____.

A

SA node; AV node

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6
Q

How is the AV node regulated so it fires more slowly than the SA node?

A

these cells are triggered by the SA node APs, even though they could spontaneously fire

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7
Q

What is the Nernst Potential of Na?

A

+58

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7
Q

What is responsible for the rapid rising phase of fast APs?

A

the Na channel

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8
Q

What is an inactivation gate?

A

a special block of the Na or K channel that functions to keep the cell in a depolarized state, even though the activation gate is open

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8
Q

What is the Na channel called? How is it inactivated?

A

Na v 1.5; voltage-dependent inactivation

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8
Q

The ___ and ____ channels generate inward current.

A

Na, Ca

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8
Q

How are the time-dependent cation current K channels evoked?

A

hyperpolarization

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9
Q

HERG produces ____.

A

I Kr

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10
Q

What is the essential signaling molecule for contraction in the heart?

A

Ca++

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10
Q

What is the opening of the gate called?

A

activation

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10
Q

What are the the time-dependent cation current channels permeable to?

A

K and Na

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10
Q

What channel is regulated by parasympathetic tone and, when activated, slows down the heart rate?

A

I kach (GIRK tetramer)

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11
Q

What potassium channel, when mutated, can predispose the pt to a prolonged QT?

A

I ks (KvLQT1 tetramer + mink), the slow delayed rectifier

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12
Q

What is the difference between the fast and slow APs?

A

the rising phase

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13
Q

Heart rate is controlled by ____ in the ____.

A

pacemaker cells; SA node

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14
Q

What is the deactivation process?

A

closing of the gate

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15
Q

What does the funny current do?

A

it causes sufficient depolarization to turn on the L-type Ca channels

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16
Q

Current flowing into the cell causes ___.

A

depolarization

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16
Q

What generates phase zero of the slow cardiac AP?

A

activation of the T-type Ca++ channels (I Ca-T) and some L-type Ca++ channels (I Ca-L)

18
Q

What modulates the rate of SA node firing?

A

the ANS

19
Q

The direction of propagation is controlled by gap junction position and by _____.

A

connective tissue insulation

20
Q

What are ectopic pacemakers?

A

any cell that is spontaneously starting the heartbeat, other than the SA node

21
Q

What is the Nernst Potential of Ca?

A

+124

22
Q

What are the time-dependent cation current K channels?

A

If or Ih

23
Q

Propagation of the AP occurs within the ____ and via ____.

A

myocardium; specialized conduction pathways

25
Q

If Vm

A

into the cell

26
Q

What generates phase one of the fast cardiac AP?

A

the transient outward current (I kto)

28
Q

The direction of the current flow depends on _____ and _____ (Nernst Potential).

A

membrane potential (Vm); ion gradient (Eion)

30
Q

The ____ is the only place where APs can propagate from the SA node to the ventricles.

A

AV node

31
Q

The L-type channels are important because ____.

A

there are known mutations associated with them that cause disease

32
Q

What is the rapid delayed rectifier potassium channel?

A

I kr (HERG tetramer + miRP1)

34
Q

If Vm>Eion, current flows ____.

A

out of the cell

35
Q

What generates phase four of the fast cardiac AP?

A

the inward rectifier current (I k1)

37
Q

Current flowing out of a cell causes ______.

A

hyperpolarization

38
Q

If _____, current flows into the cell.

A

Vm

39
Q

What is the difference between phase 4 in the fast and slow cardiac AP?

A

in slow, phase 4 is not stable

40
Q

What are the 5 phases of the fast cardiac AP?

A
  1. zero 2. one 3. two 4. three 5. four
41
Q

Cardiac APs are divided into 2 types: ___ and ___.

A

fast; slow

42
Q

How many time-dependent potassium current channels are there?

A

3

43
Q

If the cell is hyperpolarized, it has a more ___ charge.

A

negative

44
Q

The pumping of the heart depends upon propagation of the AP from the _____ to other regions.

A

SA node

45
Q

If ____, current flows out of the cell.

A

Vm>Eion

47
Q

Cell to cell propagation occurs thru ____.

A

gap junctions

48
Q

What generates phase three of the fast cardiac AP?

A

activation of the delayed rectifier current (I kr and I ks)

49
Q

Name the 2 inward rectifier K current channels.

A
  1. I k1 (KIR) 2. I Kach (GIRK)
50
Q

What are the phases of the slow cardiac AP?

A

phase zero, phase 3, phase 4

51
Q

HERG can be blocked by _____, and its blockage is pro-_____.

A

diverse compounds; arrhythmic

52
Q

____ is an “anti-target” tested in preclinical evaluation of new drugs.

A

HERG

54
Q

**** Important to know: Fast and slow cardiac APs are generated in different areas of the heart.

A

Just know this- possible exam question

56
Q

What channels produce the outward current?

A

K

57
Q

What is the intrinsic repetitive firing rate of the SA node?

A

100 bpm

58
Q

What is HERG important for?

A

duration of slow and fast APs

59
Q

What generates phase zero of the fast cardiac AP?

A

rapidly activating/inactivating Na current (I Na)

60
Q

What is the Nernst Potential of K?

A

-90

61
Q

Ion channels are _____ made of ____ that have the ability to be opened or closed, called ____.

A

little pores in the membrane; proteins; gated

62
Q

What generates phase two of the fast cardiac AP?

A

the calcium current (I Ca-L)

CVPR Exam I (29 decks)

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