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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
What generates phase zero of the slow cardiac AP?
activation of the T-type Ca++ channels (I Ca-T) and some L-type Ca++ channels (I Ca-L)
18
What modulates the rate of SA node firing?
the ANS
19
The direction of propagation is controlled by gap junction position and by \_\_\_\_\_.
connective tissue insulation
20
What are ectopic pacemakers?
any cell that is spontaneously starting the heartbeat, other than the SA node
21
What is the Nernst Potential of Ca?
+124
22
What are the time-dependent cation current K channels?
If or Ih
23
Propagation of the AP occurs within the ____ and via \_\_\_\_.
myocardium; specialized conduction pathways
25
If Vm
into the cell
26
What generates phase one of the fast cardiac AP?
the transient outward current (I kto)
28
The direction of the current flow depends on _____ and _____ (Nernst Potential).
membrane potential (Vm); ion gradient (Eion)
30
The ____ is the only place where APs can propagate from the SA node to the ventricles.
AV node
31
The L-type channels are important because \_\_\_\_.
there are known mutations associated with them that cause disease
32
What is the rapid delayed rectifier potassium channel?
I kr (HERG tetramer + miRP1)
34
If Vm\>Eion, current flows \_\_\_\_.
out of the cell
35
What generates phase four of the fast cardiac AP?
the inward rectifier current (I k1)
37
Current flowing out of a cell causes \_\_\_\_\_\_.
hyperpolarization
38
If \_\_\_\_\_, current flows into the cell.
Vm
39
What is the difference between phase 4 in the fast and slow cardiac AP?
in slow, phase 4 is not stable
40
What are the 5 phases of the fast cardiac AP?
1. zero 2. one 3. two 4. three 5. four
41
Cardiac APs are divided into 2 types: ___ and \_\_\_.
fast; slow
42
How many time-dependent potassium current channels are there?
3
43
If the cell is hyperpolarized, it has a more ___ charge.
negative
44
The pumping of the heart depends upon propagation of the AP from the _____ to other regions.
SA node
45
If \_\_\_\_, current flows out of the cell.
Vm\>Eion
47
Cell to cell propagation occurs thru \_\_\_\_.
gap junctions
48
What generates phase three of the fast cardiac AP?
activation of the delayed rectifier current (I kr and I ks)
49
Name the 2 inward rectifier K current channels.
1. I k1 (KIR) 2. I Kach (GIRK)
50
What are the phases of the slow cardiac AP?
phase zero, phase 3, phase 4
51
HERG can be blocked by \_\_\_\_\_, and its blockage is pro-\_\_\_\_\_.
diverse compounds; arrhythmic
52
\_\_\_\_ is an "anti-target" tested in preclinical evaluation of new drugs.
HERG
54
\*\*\*\* Important to know: Fast and slow cardiac APs are generated in different areas of the heart.
Just know this- possible exam question
56
What channels produce the outward current?
K
57
What is the intrinsic repetitive firing rate of the SA node?
100 bpm
58
What is HERG important for?
duration of slow and fast APs
59
What generates phase zero of the fast cardiac AP?
rapidly activating/inactivating Na current (I Na)
60
What is the Nernst Potential of K?
-90
61
Ion channels are _____ made of ____ that have the ability to be opened or closed, called \_\_\_\_.
little pores in the membrane; proteins; gated
62
What generates phase two of the fast cardiac AP?
the calcium current (I Ca-L)

CVPR Exam I (29 decks)

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