Cardiac Resting Membrane and Action Potential Flashcards Preview

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Flashcards in Cardiac Resting Membrane and Action Potential Deck (12)
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1

Describe the sequence of electrical conduction in the heart.

Na+ influx leads to conduction -> SA node activation -> Atrial activation -> AV node activation -> His-Purkinje Bundle -> Ventricular activation -> Ventricular Contraction

2

How does hyperkalemia affect the resting membrane potential?

High extracellular [K+] will increase the resting membrane potential and depolarize the cell as a result. The inside of the cell retains more K+ ions.

3

How does hypokalemia affect the resting membrane potential?

The resting membrane potential is not changed much by hypokalemia due to two factors:

-Small Na+ influx that stabilizes the membrane potential
-Inward rectification as the permeability of K+ is decreased due to iK1 blocks that occurs as the driving force on K+ increases

4

How does the K+ permeability change with hyperkalemia?

It increases

5

How does the K+ permeability change with hypokalemia?

It decreases

6

What is inward rectification and when does it occur?

It is a decrease in K+ permeability that occurs when either the electrical or chemical driving force on K+ is increased.

1) Hypokalemia
2) Depolarization of the membrane

7

What is the range for hyperkalemia?

> 5 meq/L

8

What is the range for hypokalemia?

Less than 3 meq/L

9

What is responsible for the fast response of the action potentials?

Na+ Channels

10

What is responsible for the slow response of the action potentials?

Ca2+ Channels
K+ Channels (iK/iK1/iTO)

11

How can fast responses be converted into slow responses?

Fast responses can be blocked by a toxin such as tetrodotoxin which blocks Na channels. Only the slow channels like the Ca2+ channels are left unaffected. As a result, the fast upstroke disappears and only the slow Ca response remains.

12

Why is the LV thicker and stronger than the RV?

Systemic resistance is much higher than pulmonary resistance.

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