Chapter 1.b Concept Review: Action Potential - Pacemaker Cell Flashcards Preview

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Flashcards in Chapter 1.b Concept Review: Action Potential - Pacemaker Cell Deck (12)
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1

how many phases is action potential of pacemaker cells divided into?

3; phases 0, 3, and 4

2

what distinguishes pacemaker cells from myocardial cells?

spontaneous phase 4 depolarization (upsloping phase 4)

3

which electrolyte slowly results in gradual rise of membrane potential towards its threshold potential?

slow influx of Na+

4

current responsible for phase 4 depolarization is AKA

pacemaker current or funny current (I(f))

5

once threshold potential is attained, which electrolyte causes depolarization of the cell during phase 0?

influx of Ca++

6

which electrolyte channel is opened, and which electrolyte channel is closed during repolarization, phase 3?

- efflux of K+
- closure of Ca++ channels

7

what happens when the membrane potential returns to its resting potential?

Na+ channels IMMEDIATELY open again

8

how is phase 4 directly affected?

sympathetic and parasympathetic tone

9

how does sympathetic stimulation affect phase 4?

steeper phase 4, and faster heart rate

10

how does norepinephrine affect the membrane's permeability?

increases permeability to Na+

11

what decreases the slope of phase 4 and, consequently, the HR?

vagal tone

12

what increases the cell membrane's permeability to K+ while decreasing its permeability to Na+?

ACh release by the vagus nerve