Cardiac Ion Channels & Action Potentials Flashcards Preview

Cardiovascular Unit 1 > Cardiac Ion Channels & Action Potentials > Flashcards

Flashcards in Cardiac Ion Channels & Action Potentials Deck (17):
1

What modulates the Sinoatrial Node? How fast does the SA node fire?

Modulated by ANS
~100/min

2

Parasympathetic tone slows the SA node to _________ /min

60-80

3

Both the AV node and SA node are capable of spontaneous activity. Which one "controls" the heart rate? What is this process called?

SA node action potentials control AV action potentials.

This is called "overdrive suppression." SA node spontaneously depolarizes faster than AV node.

4

In order for an action potential to propagate from the SA node to the Ventricles, it must first pass through_______

The AV node.

5

How are Fast and Slow Action potentials different?
(think of what a graph of each would look like)

SLOW:
1. No steady resting potential.
2. Rising phase is slow.
3. No plateau

FAST
1. Longer Plateau phase (caused by Ca++ ions entering cell)
2. Steady diastolic potential.
3. Fast rising phase.

6

Where are slow APs found?

1. SA node (pacemaker cells)

2. AV node

7

Where are fast APs found?

Atrial Muscle,
Perkinje Muscle,
Ventricular Muscle.

8

There are 5 phases in a fast cardiac action potential. Name them and what happens during each phase.

*Test questions WILL come from these NC*

Phase 0: Depolarization (Rising phase)
Phase 1: Partial Repolarization during plateau
Phase 2: Plateau
Phase 3: Repolarization
Phase 4: Steady Resting Potential

9

What generates the depolarization in Phase 0 of a fast cardiac action potential?
*TQ*

Sodium influx (I-Na)

I stands for current

10

What causes the plateau in Phase 2 of a fast cardiac action potential?
*TQ*

Calcium Influx (I- Ca-L)

11

What causes the slight repolarization in Phase 1 of a fast cardiac action potential?
*TQ*

Potasium efflux via I-Kto channel

*transient outward potassium current*

12

What causes the repolarization in Phase 3 of a fast cardiac action potential?
*TQ*

I-K Rapid and Slow channels (IKr and IKs) allow potassium to flow out.

This is known as the *Delayed Rectifier Current*

13

What causes the stabilization in Phase 4 of a fast cardiac action potential?
*TQ*

Ik1

This is known as the *Inward Rectifier Current*

14

What are the phases of a slow cardiac action potential?
*TQ*

Phase 0: Depolarization
Phase 3: Repolarization
Phase 4: Gradual depolarization (not steady)

15

Phase 0 of the slow cardiac AP is produced by...
*TQ*

Calcium channels turning on and off again,

16

Phase 3 of the slow cardiac AP is produced by...
*TQ*

Delayed Rectifier current (IKr and IKs)

17

Phase 4 of the slow cardiac AP is produced by...*TQ*

Funny Current (If). Produced by hyperpolarization and causes the upward creep of the slow cardiac AP.

This is involved in pacemaking.