The Cardiac Action Potential Flashcards

1
Q

Types of Potassium Channels (5)

A

I (k1) - Inward Rectifier
I (TO1) - Transient Outward
I (KS, KR, KUR)-Delayed Rectifier
slow, rapid, ultra-rapid

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2
Q

Explain I (k1) - Inward Rectifier (always open )

A

allows K+ diffusion mostly inward. If mV is less than -95mV (in).
If mV is greater than -95mV (out - loses functionality as membrane gets +

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3
Q

Phase 0 - Depolarization

A

1) Na+ (voltage gated) - Activate
2) Calcium (T-Type) - Activate
3) K+ (inward rectifier) - Inactivate

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4
Q

Phase 1 - Early Repolarization

A

1) Na+ (voltage gated) - Inactivate
2) K+ (transient outward)-Activate
3) Calcium (L-Type) - Activated

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5
Q

Phase 2 - Mid Repolarization

A

1) I (TO1) - Inactivate
2) Calcium (L-Type) - Activated
3) I (KS, KR, KUR) - Activated
4) Na-Ca - Activated

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6
Q

Why is the Na-Ca channel activated?

A

High intracellular Ca++ concentration activates the exchanger, pushing 3 Na+ into cell and 1 Ca++ out (more +)

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7
Q

Phase 3 - Repolarization, 4 - Resting Potential

A

1) I (K1) - Activating (see graph, 4*)
2) Calcium (L-Type) - inactivate
3) I (K**S, KR, KUR) - Activated
4) Na-Ca - inactivated

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8
Q

Rectifier

Transient

A

Rectifier - To make right

Transient - Lasting Short time

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9
Q

Define Inactivation & Deactivation

A
  1. Inactivation gate closes

2. Activation gate closes

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10
Q

At low mV activation gates are _______, inactivation gates are _______, High mV?

Think of figure:

A

closed, open

open , closed

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11
Q

Gimme Distribution of Channels

A

mostly same, Delayed rectifier I(kur) in atria more than ventricles,

Ca (t-type) - mostly in SA, AV nodes

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12
Q

How do Action potentials of the atrium and ventricle differ

A

More pronounced (shorter) P1 phase because of increased expression of I (kur) on the atrium

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13
Q

Phase 4 (SA, AV)

A

1) I(f - funny (PM)) - non specific ion channel - opens at low voltage
- -> Depolarization
2) I (k1) - resist depolarization
3) Ca ++ (T- Type) - open late –> D

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14
Q

Phase 0 (SA, AV)

A

1) Ca++ (T- Type) - open late –> D
2) Ca++ (L - Type) - open late –> D

*no Na++ –> slower AP - not as many Calcium channels

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15
Q

Phase 3 (SA, AV) II

A

I(k1) opens –> repolarization

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16
Q

What causes AV nodal Delay

A

CA++ channels are slower, fewer gap junctions.

17
Q

Clinical Correlation - Explain MI and how it lead to scarring, how that can cause arrhythmias

A

– See page 49

18
Q

What are the Modulatory (regulatory) channels of the heart

A

I (k-ach) - in SA, AV nodes; Open at REST with parasympathetic stimulation,

I (k-atp) - Preserver of ATP, opens when low ATP

Both resist depolarization, lower heart rate (hyperpolarization)

I (Cl,camp) - brings mp back to rest during plateau in toward -55mV E(Cl)

19
Q

What potassium channels are stimulated by the PNS, CNS

A

PARA- I (k-ach) - in SA, AV nodes; Open at REST with PS stimulation, resists depolarization/contraction

I (K s, r, ur) Delayed Rectifier -
more open at re-polarization with S stimulation, Shortens AP, increased rate!!!

20
Q

What causes the slow graded response in smooth muscle tissue?

A
  • large synapses - varicosities
  • Signaling molecules diffuse to signal
  • B1, A, musk.. receptors are spread out.
21
Q

Describe I (K1)

A

Inward Rectifier - Potassium channels.

Only brings K+ in at very neg. mV (which is never). between -95 to 0, it pushes potassium out of the cell making the cell inside more (negative) – Resisting Depolarization