Cardiac Action Potentials Flashcards

1
Q

What is the major cause of depol in neural AP

A

Na VGC

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2
Q

What channels maintain the RMP of a cell

A

K leak channels

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3
Q

What channels cause a repol of cell

A

Opening of K VGC

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4
Q

How does the AP from the Av node down travel

A

Through the IVS and back up to the atria

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5
Q

Which part of the heart receives action potential from depol first

What about for repol

A

Depol - endocardium first

Repol - epicardium first

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6
Q

Larger fibers have what in terms of transmission speed

A

Greater velocity

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7
Q

Which part of the electrical conduction system has the fastest conduction velocity

A

The purkinkie and atrial pathways

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8
Q

What does the delay at the AV Node allow for

A

Atria to completely empty into the ventricles before ventricular contraction

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9
Q

What is the RMP of ventricular and atrial myocytes compared to the SA Node and what does this mean

A

Vent/atria = -90

SA Node = -65

SA Node can depol much easier than myocytes

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10
Q

Define Na (M)

Activated when:
Action:
Phase:

A

Sodium VGC

Activated when: membrane potential crosses threshold

Action: opens very fast to allow for depol, then automatically closes (inactive gate) to allow for partial repol

Phase: 0 & 1

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11
Q

Define K(a)

Activated when:
Action:
Phase:

A

Potassium VGC

Activated when: cell depolarizes

Action:opens very rapidly, allowing for partial repol.

Phase: 1

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12
Q

Define Ca(L)

Activated when:
Action:
Phase:

A

Calcium VGC

Activated when: cell depol

Action: opens slowly and remains open to allow for prolonged plateau of phase 2. Closes allowing for phase 3 and repol.

Phase: 2 & 3

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13
Q

Define K(b) channel

Activated when:
Action:
Phase:

A

Activated when: cell depol.

Action: closes slowly and remains closed until it opens in phase 2, assisting with repol in phase 3

Phase: 2 & 3

Aka special rectifiers

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14
Q

Define K(c)

Activated when:
Action:
Phase:

A

Activated when: remains open

Action: maintains RMP

Phase: 4

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15
Q

Define Na(f)

Activated when:
Action:
Phase:

A

Activated when: SA or AP repol.

Action: opens to cause slow depol during resting phase (to get up to threshold for Na(m) to depol fully)

Phase: 4

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16
Q

The SA node depols faster or slower than other regions

A

Slower

17
Q

What is the phase 4 build-up due to in the SA Node

A

Funny voltage-gated Na(f) channels

18
Q

In the SA Node, what causes phase 0 and what is the significance of this

A

The opening of slow Ca channels and closing of special K(b) channels

This is the balancing act of Ca in and K out

19
Q

What are the special K(b) channels in the SA node sensitive to

A

AcH (parasympathetic)

20
Q

What causes phase 3 in the SA and AV nodes

A

The closing of Ca gates and opening of the K(b) gates

21
Q

Phase 4 in cardiac myocyte sis sustained by what

A

K(c)

22
Q

Define phase 1 of myocytes

A

A small repol caused by the closing of Na (m) and some K(a) opening

23
Q

When do the inactivation gates of Na VGC close

A

Phase 1

24
Q

What causes phase 2 in the myocytes

A

Slow opening of Ca VGC and closing of special K(b) channels

25
Q

What causes phase 3 in the myocytes

A

Ca VGC closing and K(b) opening

26
Q

Define chronotropic and it’s positive and negative affects

A

Changes the rate of depol of SA node and HR

Positive = faster
Negative = slower
27
Q

Define dromotropic and it’s pos. And neg. affects

A

The speed of conduction

Positive = increased speed

Negative = decreased

28
Q

Define inotropic

A

Changes the strength of muscular contraction

29
Q

Define lusitropic

A

Changes the rate of muscular relaxation

30
Q

What is the parasympathetic stimulus carried by

A

The vagus N.

31
Q

The vagus N. Carries signal to what

A

The SA and AV Nodes

32
Q

What are the chronotropic and dromotropic effects of paraympathetic

A

Chronotropic (-)
Slowed opening of Na(f) channels during phase 4

Hyperpol by increasing outward K current via K-Ach channel

Dromotropic (-)
Reduced Ca inward current
Increased outward K currents via K-Ach channel

33
Q

What are the chronotropic and dromotropic effects of sympathetic stimulation

A

Chronotropic (+)
Increased opening of Na (f) channels during phase 4

Increased Ca current

Dromotropic (+)
Increased Ca inward during phase 2

34
Q

What occurs in phase 0 of SA/AV Node AP that allows for Depol

A

Ca opens allows Ca into cell

K(b) closes which allows for buildup of Na to depol the cell.