ion question

[HiddenTruth]

So, which one is it.

1. Phase 4 of SA node is depolarized by alow Na influx, or slow influx of K and Ca? (latter, according to kaplan; first from BRS)?

2. Also, Parasymp work by increasing phase 3 repolarization, thus, taking longer for it to reach threshold (kaplan), or decrease phase 4 depolarization by decreasing Na influx (BRS)?

Thanks

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[Row Jimmy]

So, which one is it.

1. Phase 4 of SA node is depolarized by alow Na influx, or slow influx of K and Ca? (latter, according to kaplan; first from BRS)?

2. Also, Parasymp work by increasing phase 3 repolarization, thus, taking longer for it to reach threshold (kaplan), or decrease phase 4 depolarization by decreasing Na influx (BRS)?

Thanks

1. They call it the "funny phase or current" or something like that. I believe they do not have it competely figured out yet (just like autoregulation) but they think it is due to slow Na influx and/or decrease in K conductance

2. I'm going with Kaplan and hyperpolorizing cell by increasing K conductance.